feat: add scheduled message polling for avatar takeover

Add APScheduler BackgroundScheduler to on_startup that polls
takeover_service.poll_and_process_messages every 10 seconds. Added
redis and apscheduler dependencies. Added poll_and_process_messages,
fetch_unread_messages, and process_message methods to TakeoverService.
Scheduler initialization is graceful — Redis/Box IM failures do not
prevent app startup.

digital-avatar-app/backend/main.py

@@ -2,6 +2,11 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 import os
+import logging
+
+from apscheduler.schedulers.background import BackgroundScheduler
+from apscheduler.triggers.interval import IntervalTrigger
+import redis as redis_lib
 
 from database import init_db, SessionLocal
 from models import Avatar, Authorization, Organization, TokenAccount, TokenPlan
@@ -15,6 +20,8 @@ import routers.huihui_auth
 import routers.chat
 from responses import ok
 
+logger = logging.getLogger(__name__)
+
 app = FastAPI(title="会会数字分身 API", version="1.0.0")
 
 app.add_middleware(
@@ -103,3 +110,41 @@ def seed():
 def on_startup():
     init_db()
     seed()
+
+    # --- Takeover scheduler ---
+    try:
+        # Initialize Redis (optional)
+        redis_client = None
+        redis_url = os.getenv("REDIS_URL", "")
+        if redis_url:
+            try:
+                redis_client = redis_lib.from_url(redis_url)
+                redis_client.ping()
+            except Exception as e:
+                logger.warning(f"Redis connection failed, delayed takeover will degrade to immediate: {e}")
+
+        # Initialize Box IM client
+        from services.boxim_client import BoxIMClient
+        boxim_config = {
+            "HUIHUI_IM_BASE_URL": os.getenv("HUIHUI_IM_BASE_URL", "http://192.168.1.200:60040"),
+            "HUIHUI_APP_ID": os.getenv("HUIHUI_APP_ID", ""),
+            "HUIHUI_ACCESS_ID": os.getenv("HUIHUI_ACCESS_ID", ""),
+            "HUIHUI_ACCESS_SECRET": os.getenv("HUIHUI_ACCESS_SECRET", ""),
+        }
+        boxim_client = BoxIMClient(boxim_config)
+
+        # Initialize takeover service
+        from services.takeover_service import TakeoverService
+        takeover_service = TakeoverService(SessionLocal(), boxim_client, redis_client)
+
+        # Start periodic polling job
+        scheduler = BackgroundScheduler()
+        scheduler.add_job(
+            takeover_service.poll_and_process_messages,
+            trigger=IntervalTrigger(seconds=10),
+            id="takeover_message_poll",
+        )
+        scheduler.start()
+        logger.info("Takeover message polling scheduler started (interval=10s)")
+    except Exception as e:
+        logger.warning(f"Failed to initialize takeover scheduler, app will continue without it: {e}")