feat(knowledge): 任务队列、独立 worker 与 pgvector 向量索引

知识处理改为数据库任务队列，独立 worker 做切块与向量化，失败可重试。

backend/app/workers/chat_auto_closer.py

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+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+import asyncio
+import sys
+import os
+from pathlib import Path
+
+# Add the parent directory to Python path to allow imports
+sys.path.append(str(Path(__file__).parent.parent.parent))
+
+from app.database import SessionLocal
+from app.repositories.session_to_agent import SessionToAgentRepository
+from app.core.logger import get_logger
+
+logger = get_logger(__name__)
+
+# Configure check interval (default to 24 hours - once a day)
+CHECK_INTERVAL = int(os.environ.get('CHAT_AUTO_CLOSE_INTERVAL', '86400'))  # 24 hours in seconds
+WORKER_ID = os.environ.get('GUNICORN_WORKER_ID', 'standalone')
+
+async def run_auto_closer():
+    """Single run of the auto closer"""
+    db = None
+    try:
+        logger.info(f"Worker {WORKER_ID}: Running chat auto-closer")
+        
+        db = SessionLocal()
+        session_repo = SessionToAgentRepository(db)
+        
+        # Auto-close inactive agent chats
+        closed_count = session_repo.auto_close_inactive_agent_chats()
+        
+        if closed_count > 0:
+            logger.info(f"Worker {WORKER_ID}: Auto-closed {closed_count} inactive agent chats")
+        else:
+            logger.info(f"Worker {WORKER_ID}: No inactive agent chats found to close")
+            
+    except Exception as e:
+        logger.error(f"Worker {WORKER_ID}: Error in chat auto-closer: {str(e)}")
+        raise
+    finally:
+        if db:
+            db.close()
+
+async def run_auto_closer_loop():
+    """Run the chat auto-closer in a continuous loop"""
+    logger.info(f"Worker {WORKER_ID}: Starting chat auto-closer with {CHECK_INTERVAL}s check interval (once per day)")
+    
+    try:
+        iteration = 0
+        
+        while True:
+            iteration += 1
+            start_time = asyncio.get_event_loop().time()
+            
+            try:
+                logger.info(f"Worker {WORKER_ID}: Iteration {iteration} - Checking for inactive agent chats...")
+                await run_auto_closer()
+                logger.info(f"Worker {WORKER_ID}: Iteration {iteration} - Auto-closer completed successfully")
+            except Exception as e:
+                logger.error(f"Worker {WORKER_ID}: Iteration {iteration} - Error in auto-closer: {str(e)}")
+            
+            # Calculate how long the processing took
+            elapsed = asyncio.get_event_loop().time() - start_time
+            logger.info(f"Worker {WORKER_ID}: Iteration {iteration} - Processing took {elapsed:.2f} seconds")
+            
+            # Sleep for the configured interval (24 hours)
+            logger.info(f"Worker {WORKER_ID}: Iteration {iteration} - Sleeping for {CHECK_INTERVAL} seconds (24 hours) before next check")
+            await asyncio.sleep(CHECK_INTERVAL)
+            
+    except Exception as e:
+        logger.error(f"Worker {WORKER_ID}: Fatal error in chat auto-closer: {str(e)}")
+        sys.exit(1)
+
+def app(environ, start_response):
+    """WSGI application for health checks"""
+    status = '200 OK'
+    headers = [('Content-type', 'text/plain')]
+    start_response(status, headers)
+    return [b'Chat Auto-Closer Worker is running']
+
+# Main entry point for running as a standalone service
+if __name__ == "__main__":
+    logger.info("Starting chat auto-closer service")
+    
+    # Run the auto-closer loop
+    asyncio.run(run_auto_closer_loop())