fix(lotw): 呼号冲突批量全阻时也进预览，呼号不符改为显示记录≠证书

整批记录都被呼号冲突挡住（0 条可传）时，统计闸门直接弹「N QSO(s) can't be uploaded」
消息并返回，带【改写为…】【换一张证书】两个动作的预览弹窗根本走不到，那批记录无从
处理。现在只要原因里有呼号冲突就放行到预览：0 条可传也出预览（显示 0 QSO(s) + 冲突
提示 + 两个动作），上传键置灰——以前点确认会返回“预览已过期”。其它原因的 0 条可传
批次保持原消息弹窗不变。

「MY callsign does not match the certificate」的示例值由某条记录的对方呼号改为
「记录呼号 ≠ 证书呼号」，把需要协调的两个值都打出来（旧文案读起来像证书呼号）。

空预览不再显示空的日期区间。

新增 LoTWUploadMessagesTest 3 例：冲突批量必须进预览、无冲突的 0 条可传批次保持消息、
有待传记录时不走冲突兜底；仓库层用例新增：全阻批量仍返回带冲突清单的预览、且无载荷
时确认安全地按“过期”失败。

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

@@ -299,7 +299,9 @@ private fun LogbookUploadPreviewDialog(
             Column(verticalArrangement = Arrangement.spacedBy(4.dp)) {
                 Text("${preview.callsign}  DXCC ${preview.dxcc}  Grid ${preview.grid}", fontSize = 13.sp)
                 Text(
-                    "${preview.count} QSO(s) · ${preview.firstUtc} – ${preview.lastUtc}",
+                    // A blocked batch (shown for its conflict actions) has no date range to show.
+                    if (preview.firstUtc.isBlank()) "${preview.count} QSO(s)"
+                    else "${preview.count} QSO(s) · ${preview.firstUtc} – ${preview.lastUtc}",
                     fontSize = 13.sp
                 )
                 if (preview.skipped > 0 || preview.unknownSkipped > 0 || preview.unavailableSkipped > 0) {
@@ -357,7 +359,9 @@ private fun LogbookUploadPreviewDialog(
             }
         },
         confirmButton = {
-            TextButton(onClick = onConfirm, enabled = !busy) {
+            // Nothing uploadable (a conflict-only batch): the actions above are the way out, so the
+            // upload button stays disabled instead of failing with an expired preview.
+            TextButton(onClick = onConfirm, enabled = !busy && preview.count > 0) {
                 Text(stringResource(R.string.prefs_logbook_upload_confirm))
             }
         },

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

@@ -46,6 +46,7 @@ import com.rtbishop.look4sat.core.domain.repository.WavelogUploadOutcome
 import com.rtbishop.look4sat.core.domain.repository.WavelogUploadPreview
 import com.rtbishop.look4sat.core.domain.usecase.IShowToast
 import com.rtbishop.look4sat.core.domain.utility.VersionComparator
+import com.rtbishop.look4sat.core.domain.logbook.needsPreviewForConflicts
 import com.rtbishop.look4sat.core.domain.logbook.resubmitCandidates
 import com.rtbishop.look4sat.core.domain.logbook.toConfirmedRecord
 import com.rtbishop.look4sat.core.domain.logbook.unavailableUploadSummary
@@ -576,7 +577,10 @@ class SettingsViewModel(
                 // LoTW-imported confirmations are the feedback side.
                 val pending = all.filter { !it.lotwConfirmed && !it.lotwUploaded && it.status == com.rtbishop.look4sat.core.domain.logbook.QsoStatus.COMPLETE }
                 val audit = lotwUploadRepository.audit(pending)
-                if (audit.pending == 0) {
+                // A batch held back only by callsign conflicts still gets the preview: that dialog
+                // carries the rewrite / use-another-certificate actions. Without this the operator
+                // gets a dead-end message and those records can never be uploaded.
+                if (audit.pending == 0 && !audit.needsPreviewForConflicts()) {
                     val msg = when {
                         audit.unavailable > 0 -> com.rtbishop.look4sat.core.domain.logbook.unavailableUploadSummary(
                             audit.unavailable, audit.reasons, audit.details, audit.duplicates, audit.incomplete