feat: add message reliability foundation

- implement idempotent message creation via client_message_id

- add persistent delivered/read receipts

- expose /messages/status and wire websocket receipt events

- update web client to send client ids and auto-ack delivered/read

app/messages/router.py

@@ -3,8 +3,9 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.auth.service import get_current_user
 from app.database.session import get_db
-from app.messages.schemas import MessageCreateRequest, MessageRead, MessageUpdateRequest
+from app.messages.schemas import MessageCreateRequest, MessageRead, MessageStatusUpdateRequest, MessageUpdateRequest
 from app.messages.service import create_chat_message, delete_message, get_messages, update_message
+from app.realtime.schemas import MessageStatusPayload
 from app.realtime.service import realtime_gateway
 from app.users.models import User
 
@@ -18,7 +19,11 @@ async def create_message(
     current_user: User = Depends(get_current_user),
 ) -> MessageRead:
     message = await create_chat_message(db, sender_id=current_user.id, payload=payload)
-    await realtime_gateway.publish_message_created(message=message, sender_id=current_user.id)
+    await realtime_gateway.publish_message_created(
+        message=message,
+        sender_id=current_user.id,
+        client_message_id=payload.client_message_id,
+    )
     return message
 
 
@@ -50,3 +55,17 @@ async def remove_message(
     current_user: User = Depends(get_current_user),
 ) -> None:
     await delete_message(db, message_id=message_id, user_id=current_user.id)
+
+
+@router.post("/status")
+async def update_status(
+    payload: MessageStatusUpdateRequest,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> dict[str, int]:
+    return await realtime_gateway.handle_message_status(
+        db,
+        user_id=current_user.id,
+        payload=MessageStatusPayload(chat_id=payload.chat_id, message_id=payload.message_id),
+        event=payload.status,
+    )