feat: add reply/forward/pin message flow across backend and web

- add reply_to/forwarded_from message fields and chat pinned_message field

- add forward and pin APIs plus reply support in message create

- wire web actions: Reply, Fwd, Pin and reply composer state

- fix spam policy bug: allow repeated identical messages, keep rate limiting

app/messages/service.py

@@ -6,12 +6,16 @@ from app.chats.service import ensure_chat_membership
 from app.messages import repository
 from app.messages.models import Message
 from app.messages.spam_guard import enforce_message_spam_policy
-from app.messages.schemas import MessageCreateRequest, MessageStatusUpdateRequest, MessageUpdateRequest
+from app.messages.schemas import MessageCreateRequest, MessageForwardRequest, MessageStatusUpdateRequest, MessageUpdateRequest
 from app.notifications.service import dispatch_message_notifications
 
 
 async def create_chat_message(db: AsyncSession, *, sender_id: int, payload: MessageCreateRequest) -> Message:
     await ensure_chat_membership(db, chat_id=payload.chat_id, user_id=sender_id)
+    if payload.reply_to_message_id is not None:
+        reply_to = await repository.get_message_by_id(db, payload.reply_to_message_id)
+        if not reply_to or reply_to.chat_id != payload.chat_id:
+            raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY, detail="Invalid reply target")
     if payload.client_message_id:
         existing = await repository.get_message_by_client_message_id(
             db,
@@ -30,6 +34,8 @@ async def create_chat_message(db: AsyncSession, *, sender_id: int, payload: Mess
             db,
             chat_id=payload.chat_id,
             sender_id=sender_id,
+            reply_to_message_id=payload.reply_to_message_id,
+            forwarded_from_message_id=None,
             message_type=payload.type,
             text=payload.text,
         )
@@ -167,3 +173,29 @@ async def mark_message_status(
         "last_delivered_message_id": receipt.last_delivered_message_id or 0,
         "last_read_message_id": receipt.last_read_message_id or 0,
     }
+
+
+async def forward_message(
+    db: AsyncSession,
+    *,
+    source_message_id: int,
+    sender_id: int,
+    payload: MessageForwardRequest,
+) -> Message:
+    source = await repository.get_message_by_id(db, source_message_id)
+    if not source:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Source message not found")
+    await ensure_chat_membership(db, chat_id=source.chat_id, user_id=sender_id)
+    await ensure_chat_membership(db, chat_id=payload.target_chat_id, user_id=sender_id)
+    forwarded = await repository.create_message(
+        db,
+        chat_id=payload.target_chat_id,
+        sender_id=sender_id,
+        reply_to_message_id=None,
+        forwarded_from_message_id=source.id,
+        message_type=source.type,
+        text=source.text,
+    )
+    await db.commit()
+    await db.refresh(forwarded)
+    return forwarded