feat: Upgrade Global Presence to SSE architecture

- matrix-presence-aggregator v2 with SSE endpoint
- Created @presence_daemon Matrix user
- SSE proxy in Next.js /api/presence/stream
- Updated frontend to use SSE instead of WebSocket
- Real-time city online count and room presence

services/matrix-presence-aggregator/app/models.py

@@ -0,0 +1,24 @@
+"""Data models for Presence Aggregator"""
+from pydantic import BaseModel
+from typing import List
+from datetime import datetime
+
+
+class RoomPresence(BaseModel):
+    room_id: str          # internal room id from DB
+    matrix_room_id: str   # Matrix room ID (!xxx:domain)
+    online: int
+    typing: int
+
+
+class CityPresence(BaseModel):
+    online_total: int
+    rooms_online: int
+
+
+class PresenceSnapshot(BaseModel):
+    type: str = "presence_update"
+    timestamp: datetime
+    city: CityPresence
+    rooms: List[RoomPresence]
+