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。

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/logbook/IQsoRepository.kt

@@ -22,7 +22,14 @@ interface IQsoRepository {
      * signed with (1–4 gridsquares: inside a grid / on a line / on a corner), so the
      * logbook row can show which grids the QSO went out under.
      */
-    suspend fun markUploaded(ids: List<Long>, grids: List<String> = emptyList())
+    suspend fun markUploaded(ids: List<Long>, grids: List<String> = emptyList(), certificateCallsign: String = "")
+
+    /**
+     * Rewrites the operator's callsign on the given records. This is the answer to "these contacts
+     * were logged under another certificate — upload them under the one installed now". Returns the
+     * number of records that changed.
+     */
+    suspend fun rewriteMyCallsign(ids: List<Long>, callsign: String): Int
 
     /**
      * Marks the batch as uploaded to Wavelog (independent of the LoTW upload state) and

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/repository/ILoTWUploadRepository.kt

@@ -107,7 +107,13 @@ data class LoTWUploadPreview(
     val grids: List<String> = emptyList(),
     /** True when this batch is a resubmit: already-uploaded/confirmed records were allowed
      *  through so the corrected station location reaches LoTW as an update of the contact. */
-    val resubmit: Boolean = false
+    val resubmit: Boolean = false,
+    /** Records in this batch whose own callsign is blank (logged before a certificate was
+     *  installed). They are signed with [callsign]; a successful upload writes it into them. */
+    val missingCallsign: Int = 0,
+    /** Records refused because they name a different own callsign than [callsign]. The upload
+     *  flow offers either rewriting them with [callsign] or using the other certificate. */
+    val callsignConflicts: List<Long> = emptyList()
 )
 
 /** Pre-upload location check: the freshest known position grid is not covered by the