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/realtime/schemas.py

@@ -25,6 +25,7 @@ class SendMessagePayload(BaseModel):
     text: str | None = Field(default=None, max_length=4096)
     temp_id: str | None = None
     client_message_id: str | None = Field(default=None, min_length=8, max_length=64)
+    reply_to_message_id: int | None = None
 
 
 class ChatEventPayload(BaseModel):

app/realtime/service.py

@@ -86,6 +86,7 @@ class RealtimeGateway:
                 type=payload.type,
                 text=payload.text,
                 client_message_id=payload.client_message_id or payload.temp_id,
+                reply_to_message_id=payload.reply_to_message_id,
             ),
         )
         await self.publish_message_created(