fix(lotw): 空呼号记录按证书上传并回填，呼号冲突可选改写或换证书

证书装好之前记录的 QSO 自己呼号存空，签名时被判 CALLSIGN_MISMATCH，整批上传失败。
现在这类记录改用当前证书呼号签名，不再拒签：预览提示「其中 N 条记录没有呼号，将按证书
XXX 上传」，上传成功后仅把这些记录的空呼号回填为证书呼号（只填空值，经 save() 写入以
保持去重键一致，不动时间/频率/模式/对方呼号/上传状态与确认状态）。

自己呼号非空且与证书不同的记录仍拒签（不冒签他人记录），但预览给出两个选择：
「改写为 XXX」把冲突记录的自己呼号改成当前证书呼号后即可重传；「换一张证书」在设置页
关掉日志本并打开 LoTW 配置导入另一张证书（雷达页提示去设置页导入）。

新增单测：空呼号签名与计数、冲突记录 id、markUploaded 只填空值、rewriteMyCallsign 只改
冲突记录；并修正测试夹具 MemStorage.read 返回共享数组（被调用方 fill(0) 后破坏已存证书，
与文件存储行为不一致）导致的问题。

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/LogPage.kt

@@ -262,7 +262,9 @@ fun LogPage(
                 preview = preview,
                 busy = logUiState.busy,
                 onConfirm = logViewModel::confirmUpload,
-                onDismiss = logViewModel::dismissPreview
+                onDismiss = logViewModel::dismissPreview,
+                onRewriteCallsign = logViewModel::rewriteCallsignConflicts,
+                onSwitchCertificate = logViewModel::switchCertificateForConflicts
             )
         }
     }
@@ -417,7 +419,9 @@ private fun UploadPreviewDialog(
     preview: com.rtbishop.look4sat.core.domain.repository.LoTWUploadPreview,
     busy: Boolean,
     onConfirm: () -> Unit,
-    onDismiss: () -> Unit
+    onDismiss: () -> Unit,
+    onRewriteCallsign: () -> Unit,
+    onSwitchCertificate: () -> Unit
 ) {
     AlertDialog(
         onDismissRequest = onDismiss,
@@ -464,6 +468,32 @@ private fun UploadPreviewDialog(
                     }
                     Text(parts.joinToString(" · "), fontSize = 12.sp, color = MaterialTheme.colorScheme.error)
                 }
+                if (preview.missingCallsign > 0) {
+                    // Logged while no certificate was installed; signed with the certificate's
+                    // callsign instead of being refused.
+                    Text(
+                        stringResource(R.string.prefs_logbook_callsign_missing, preview.missingCallsign, preview.callsign),
+                        fontSize = 12.sp,
+                        color = MaterialTheme.colorScheme.primary
+                    )
+                }
+                if (preview.callsignConflicts.isNotEmpty()) {
+                    // These name another callsign than the certificate: rewrite them with this
+                    // certificate's callsign, or upload them under the other certificate.
+                    Text(
+                        stringResource(R.string.prefs_logbook_callsign_different, preview.callsignConflicts.size, preview.callsign),
+                        fontSize = 12.sp,
+                        color = MaterialTheme.colorScheme.error
+                    )
+                    Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                        TextButton(onClick = onRewriteCallsign, enabled = !busy) {
+                            Text(stringResource(R.string.prefs_logbook_callsign_rewrite, preview.callsign), fontSize = 12.sp)
+                        }
+                        TextButton(onClick = onSwitchCertificate, enabled = !busy) {
+                            Text(stringResource(R.string.prefs_logbook_callsign_switch), fontSize = 12.sp)
+                        }
+                    }
+                }
                 Text(preview.contacts.joinToString("\n") { it }, fontSize = 12.sp, maxLines = 8)
             }
         },

feature/radar/src/main/java/com/rtbishop/look4sat/feature/radar/LogViewModel.kt

@@ -343,7 +343,7 @@ class LogViewModel(
             if (result is LoTWUploadResult.Accepted && lastUploadedIds.isNotEmpty()) {
                 // Mark the submitted QSOs as uploaded (distinct from confirmed) and stamp
                 // the station grids this batch went out under.
-                qsoRepository.markUploaded(lastUploadedIds, preview.grids)
+                qsoRepository.markUploaded(lastUploadedIds, preview.grids, preview.callsign)
                 lastUploadedIds = emptyList()
             }
             val msg = when (result) {
@@ -368,6 +368,34 @@ class LogViewModel(
 
     fun dismissPreview() = _uiState.update { it.copy(preview = null) }
 
+    /**
+     * Operator chose "rewrite" on the callsign conflict: the refused records get this certificate's
+     * callsign so the next upload can sign them. The prepared batch is dropped — nothing was sent.
+     */
+    fun rewriteCallsignConflicts() {
+        val preview = _uiState.value.preview ?: return
+        val ids = preview.callsignConflicts
+        if (ids.isEmpty()) return
+        viewModelScope.launch {
+            _uiState.update { it.copy(busy = true) }
+            val changed = qsoRepository.rewriteMyCallsign(ids, preview.callsign)
+            lotwUploadRepository.discardPreview()
+            lastUploadedIds = emptyList()
+            _uiState.update {
+                it.copy(busy = false, preview = null, message = "$changed record(s) rewritten to ${preview.callsign} — upload again")
+            }
+        }
+    }
+
+    /** Operator chose "use another certificate": that certificate is imported on the settings page. */
+    fun switchCertificateForConflicts() {
+        lotwUploadRepository.discardPreview()
+        lastUploadedIds = emptyList()
+        _uiState.update {
+            it.copy(preview = null, message = "Import the other callsign's certificate in Settings → LoTW upload, then upload again")
+        }
+    }
+
     fun dismissWavelogPreview() = _uiState.update { it.copy(wavelogPreview = null) }
 
     /**

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/LogbookDialog.kt

@@ -103,6 +103,10 @@ fun LogbookDialog(
     onDismissMessage: () -> Unit,
     onIgnorePositionWarning: () -> Unit = {},
     onFixGrid: (List<String>) -> Unit = {},
+    /** Rewrite the records whose own callsign differs from the certificate's. */
+    onRewriteCallsign: () -> Unit = {},
+    /** Leave the upload to import a different certificate instead. */
+    onSwitchCertificate: () -> Unit = {},
     selectionMode: Boolean = false,
     selectedIds: Set<Long> = emptySet(),
     onStartSelection: (Long) -> Unit = {},
@@ -246,7 +250,9 @@ fun LogbookDialog(
             preview = preview,
             busy = uploadBusy,
             onConfirm = onConfirmUpload,
-            onDismiss = onDismissPreview
+            onDismiss = onDismissPreview,
+            onRewriteCallsign = onRewriteCallsign,
+            onSwitchCertificate = onSwitchCertificate
         )
     }
     if (uploadMessage.isNotBlank()) {
@@ -280,7 +286,9 @@ private fun LogbookUploadPreviewDialog(
     preview: com.rtbishop.look4sat.core.domain.repository.LoTWUploadPreview,
     busy: Boolean,
     onConfirm: () -> Unit,
-    onDismiss: () -> Unit
+    onDismiss: () -> Unit,
+    onRewriteCallsign: () -> Unit,
+    onSwitchCertificate: () -> Unit
 ) {
     AlertDialog(
         onDismissRequest = onDismiss,
@@ -319,6 +327,32 @@ private fun LogbookUploadPreviewDialog(
                         color = MaterialTheme.colorScheme.primary
                     )
                 }
+                if (preview.missingCallsign > 0) {
+                    // Logged while no certificate was installed; signed with the certificate's
+                    // callsign instead of being refused.
+                    Text(
+                        stringResource(R.string.prefs_logbook_callsign_missing, preview.missingCallsign, preview.callsign),
+                        fontSize = 12.sp,
+                        color = MaterialTheme.colorScheme.primary
+                    )
+                }
+                if (preview.callsignConflicts.isNotEmpty()) {
+                    // These name another callsign than the certificate: the operator either rewrites
+                    // them with the certificate's callsign or uploads them under that other one.
+                    Text(
+                        stringResource(R.string.prefs_logbook_callsign_different, preview.callsignConflicts.size, preview.callsign),
+                        fontSize = 12.sp,
+                        color = MaterialTheme.colorScheme.error
+                    )
+                    Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                        TextButton(onClick = onRewriteCallsign, enabled = !busy) {
+                            Text(stringResource(R.string.prefs_logbook_callsign_rewrite, preview.callsign), fontSize = 12.sp)
+                        }
+                        TextButton(onClick = onSwitchCertificate, enabled = !busy) {
+                            Text(stringResource(R.string.prefs_logbook_callsign_switch), fontSize = 12.sp)
+                        }
+                    }
+                }
                 Text(preview.contacts.joinToString("\n") { it }, fontSize = 12.sp, maxLines = 8)
             }
         },

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsScreen.kt

@@ -308,6 +308,15 @@ private fun SettingsScreen(
             onConfirmUpload = { onAction(SettingsAction.ConfirmLogbookUpload) },
             onDismissPreview = { onAction(SettingsAction.DismissLogbookPreview) },
             onDismissMessage = { onAction(SettingsAction.ClearLogbookMessage) },
+            onRewriteCallsign = { onAction(SettingsAction.RewriteLogbookCallsigns) },
+            onSwitchCertificate = {
+                // The other callsign's certificate lives in the LoTW upload settings: leave the
+                // logbook and open that dialog.
+                onAction(SettingsAction.DismissLogbookPreview)
+                onAction(SettingsAction.ExitLogbookSelection)
+                dialogs.logbook = false
+                dialogs.lotwUpload = true
+            },
             onIgnorePositionWarning = { onAction(SettingsAction.IgnoreLogbookPositionWarning) },
             onFixGrid = { grids ->
                 onAction(SettingsAction.AbandonLogbookForGridFix)

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsState.kt

@@ -193,6 +193,7 @@ sealed interface SettingsAction {
     data object PrepareLogbookUpload : SettingsAction
     data object ConfirmLogbookUpload : SettingsAction
     data object DismissLogbookPreview : SettingsAction
+    data object RewriteLogbookCallsigns : SettingsAction
     /** The operator acknowledged the position mismatch and wants to upload anyway. */
     data object IgnoreLogbookPositionWarning : SettingsAction
     /** The operator chose to fix the station location first; the preview is discarded. */

feature/settings/src/main/java/com/rtbishop/look4sat/feature/settings/SettingsViewModel.kt

@@ -257,6 +257,7 @@ class SettingsViewModel(
             SettingsAction.PrepareLogbookUpload -> prepareLogbookUpload()
             SettingsAction.ConfirmLogbookUpload -> confirmLogbookUpload()
             SettingsAction.DismissLogbookPreview -> dismissLogbookPreview()
+            SettingsAction.RewriteLogbookCallsigns -> rewriteLogbookCallsigns()
             SettingsAction.IgnoreLogbookPositionWarning -> ignoreLogbookPositionWarning()
             SettingsAction.AbandonLogbookForGridFix -> abandonLogbookForGridFix()
             is SettingsAction.StartLogbookSelection -> startLogbookSelection(action.id)
@@ -648,7 +649,7 @@ class SettingsViewModel(
             val result = lotwUploadRepository.upload(preview.id)
             val accepted = result is com.rtbishop.look4sat.core.domain.repository.LoTWUploadResult.Accepted
             if (accepted && lastLogbookUploadIds.isNotEmpty()) {
-                qsoRepository.markUploaded(lastLogbookUploadIds, preview.grids)
+                qsoRepository.markUploaded(lastLogbookUploadIds, preview.grids, preview.callsign)
                 lastLogbookUploadIds = emptyList()
             }
             val msg = when (result) {
@@ -673,6 +674,29 @@ class SettingsViewModel(
 
     private fun dismissLogbookPreview() = _uiState.update { it.copy(logbookPreview = null, logbookWavelogPreview = null) }
 
+    /**
+     * Operator chose "rewrite" on the callsign conflict: the refused records get this certificate's
+     * callsign so the next upload can sign them. The batch is discarded — nothing was uploaded.
+     */
+    private fun rewriteLogbookCallsigns() {
+        val preview = _uiState.value.logbookPreview ?: return
+        val ids = preview.callsignConflicts
+        if (ids.isEmpty()) return
+        viewModelScope.launch {
+            _uiState.update { it.copy(logbookUploadBusy = true) }
+            val changed = qsoRepository.rewriteMyCallsign(ids, preview.callsign)
+            lotwUploadRepository.discardPreview()
+            lastLogbookUploadIds = emptyList()
+            _uiState.update {
+                it.copy(
+                    logbookUploadBusy = false,
+                    logbookPreview = null,
+                    logbookUploadMessage = "$changed record(s) rewritten to ${preview.callsign} — upload again"
+                )
+            }
+        }
+    }
+
     /** Operator chose "ignore" on the position check: keep the prepared preview. */
     private fun ignoreLogbookPositionWarning() = _uiState.update { it.copy(logbookPositionWarning = null) }