feat(backup): add backup record reads to FirestoreConversationDataSource (getConversationsForBackup, getBackupRecords)

app/src/main/java/app/closer/data/remote/FirestoreConversationDataSource.kt

@@ -2,6 +2,7 @@ package app.closer.data.remote
 
 import app.closer.crypto.CoupleEncryptionManager
 import app.closer.crypto.FieldEncryptor
+import app.closer.domain.model.BackupMessageRecord
 import app.closer.domain.model.Conversation
 import app.closer.domain.model.QuestionMessage
 import com.google.firebase.firestore.DocumentSnapshot
@@ -232,6 +233,58 @@ class FirestoreConversationDataSource @Inject constructor(
         return runCatching { aead.decrypt(cipher, coupleId.toByteArray(Charsets.UTF_8)) }.getOrNull()
     }
 
+    // ─── Backup reads (source of truth for the encrypted backup) ─────────────────────
+
+    /** All conversations for the couple as (id, type) — `main` + per-question threads. */
+    suspend fun getConversationsForBackup(coupleId: String): List<Pair<String, String>> =
+        runCatching {
+            conversationsRef(coupleId).get().await().documents.map {
+                it.id to (it.getString("type") ?: "main")
+            }
+        }.getOrDefault(emptyList())
+
+    /**
+     * Backup records for one conversation with a resolved `createdAt` strictly after [afterCreatedAt]
+     * (0 = from the beginning). Pending-write docs (null server timestamp) are skipped so the cursor
+     * never straddles an unresolved message. Includes tombstones + reactions for fidelity.
+     */
+    suspend fun getBackupRecords(
+        coupleId: String,
+        conversationId: String,
+        conversationType: String,
+        afterCreatedAt: Long
+    ): List<BackupMessageRecord> = runCatching {
+        var query: Query = messagesRef(coupleId, conversationId).orderBy("createdAt", Query.Direction.ASCENDING)
+        if (afterCreatedAt > 0L) {
+            query = query.whereGreaterThan("createdAt", com.google.firebase.Timestamp(java.util.Date(afterCreatedAt)))
+        }
+        query.get().await().documents.mapNotNull { it.toBackupRecord(conversationId, conversationType) }
+    }.getOrDefault(emptyList())
+
+    private fun DocumentSnapshot.toBackupRecord(
+        conversationId: String,
+        conversationType: String
+    ): BackupMessageRecord? {
+        // Skip unresolved server timestamps — back them up once they settle.
+        val createdAt = getTimestamp("createdAt")?.toDate()?.time ?: return null
+        @Suppress("UNCHECKED_CAST")
+        val reactions = (get("reactions") as? Map<String, String>).orEmpty()
+        val type = getString("type") ?: "text"
+        return BackupMessageRecord(
+            messageId = id,
+            conversationId = conversationId,
+            conversationType = conversationType,
+            authorUserId = getString("authorUserId") ?: "",
+            type = type,
+            encText = if (type == "text") getString("text") else null,
+            mediaUrl = getString("mediaUrl"),
+            durationMs = getLong("durationMs"),
+            createdAt = createdAt,
+            deleted = getBoolean("deleted") ?: false,
+            reactions = reactions
+        )
+    }
+
     // ─── Mappers / await helpers ────────────────────────────────────────────────────
 
     private fun DocumentSnapshot.toConversation(