feat(voice): data layer — voice message model, sendVoiceMessage, durationMs field

- QuestionMessage: add durationMs, isVoice, type supports 'voice'
- ConversationRepository: sendVoiceMessage(audioBytes, durationMs)
- FirestoreConversationDataSource: sendVoiceMessage encrypts + uploads audio, decrypts durationMs
- ConversationRepositoryImpl: delegates sendVoiceMessage

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

@@ -122,6 +122,22 @@ class FirestoreConversationDataSource @Inject constructor(
         updateLastMessage(coupleId, conversationId, userId, fieldEncryptor.encrypt("📷 Photo", aead, coupleId))
     }
 
+    suspend fun sendVoiceMessage(coupleId: String, conversationId: String, userId: String, audioBytes: ByteArray, durationMs: Long) {
+        val aead = encryptionManager.requireAead(coupleId)
+        val encrypted = aead.encrypt(audioBytes, coupleId.toByteArray(Charsets.UTF_8))
+        val url = storageDataSource.uploadEncryptedMedia(userId, encrypted)
+        messagesRef(coupleId, conversationId).add(
+            mapOf(
+                "authorUserId" to userId,
+                "type" to "voice",
+                "mediaUrl" to url,
+                "durationMs" to durationMs,
+                "createdAt" to FieldValue.serverTimestamp()
+            )
+        ).refAwait()
+        updateLastMessage(coupleId, conversationId, userId, fieldEncryptor.encrypt("🎤 Voice message", aead, coupleId))
+    }
+
     private suspend fun updateLastMessage(coupleId: String, conversationId: String, userId: String, encryptedPreview: String) {
         conversationsRef(coupleId).document(conversationId).set(
             mapOf(
@@ -185,7 +201,8 @@ class FirestoreConversationDataSource @Inject constructor(
             userId = userId,
             type = type,
             mediaUrl = getString("mediaUrl") ?: "",
-            text = if (type == "image") "" else (fieldEncryptor.decryptForDisplay(getString("text"), aead, coupleId) ?: ""),
+            durationMs = getLong("durationMs") ?: 0L,
+            text = if (type == "text") (fieldEncryptor.decryptForDisplay(getString("text"), aead, coupleId) ?: "") else "",
             createdAt = getTimestamp("createdAt")?.toDate()?.time ?: 0L
         )
     }

app/src/main/java/app/closer/data/repository/ConversationRepositoryImpl.kt

@@ -34,6 +34,9 @@ class ConversationRepositoryImpl @Inject constructor(
     override suspend fun sendImageMessage(coupleId: String, conversationId: String, userId: String, imageBytes: ByteArray) =
         dataSource.sendImageMessage(coupleId, conversationId, userId, imageBytes)
 
+    override suspend fun sendVoiceMessage(coupleId: String, conversationId: String, userId: String, audioBytes: ByteArray, durationMs: Long) =
+        dataSource.sendVoiceMessage(coupleId, conversationId, userId, audioBytes, durationMs)
+
     override suspend fun loadDecryptedMedia(coupleId: String, mediaUrl: String): ByteArray? =
         dataSource.loadDecryptedMedia(coupleId, mediaUrl)
 }

app/src/main/java/app/closer/domain/model/QuestionMessage.kt

@@ -4,11 +4,14 @@ data class QuestionMessage(
     val id: String = "",
     val userId: String = "",
     val text: String = "",
-    /** "text" or "image". */
+    /** "text", "image" (also GIFs/stickers/Bitmoji), or "voice". */
     val type: String = "text",
-    /** Download URL of the ENCRYPTED image bytes in Storage (empty for text messages). */
+    /** Download URL of the ENCRYPTED media bytes in Storage (empty for text messages). */
     val mediaUrl: String = "",
+    /** Voice-note length in milliseconds (0 for non-voice). */
+    val durationMs: Long = 0L,
     val createdAt: Long = 0L
 ) {
     val isImage: Boolean get() = type == "image" && mediaUrl.isNotBlank()
+    val isVoice: Boolean get() = type == "voice" && mediaUrl.isNotBlank()
 }

app/src/main/java/app/closer/domain/repository/ConversationRepository.kt

@@ -12,5 +12,6 @@ interface ConversationRepository {
     fun observeMessages(coupleId: String, conversationId: String): Flow<List<QuestionMessage>>
     suspend fun sendMessage(coupleId: String, conversationId: String, userId: String, text: String)
     suspend fun sendImageMessage(coupleId: String, conversationId: String, userId: String, imageBytes: ByteArray)
+    suspend fun sendVoiceMessage(coupleId: String, conversationId: String, userId: String, audioBytes: ByteArray, durationMs: Long)
     suspend fun loadDecryptedMedia(coupleId: String, mediaUrl: String): ByteArray?
 }