feat(file): 优化文件处理和缓存机制

- 重构文件处理逻辑，提高性能和可维护性
- 增加缓存机制，减少重复读取和处理
- 改进错误处理和日志记录
- 优化缩略图生成算法
- 添加性能监控和测试依赖

utils/db_pool.py

@@ -0,0 +1,61 @@
+import sqlite3
+import threading
+from contextlib import contextmanager
+from queue import Queue, Empty
+import app_conf
+
+class ConnectionPool:
+    def __init__(self, database_path: str, max_connections: int = 10):
+        self.database_path = database_path
+        self.max_connections = max_connections
+        self.pool = Queue(maxsize=max_connections)
+        self.lock = threading.Lock()
+        self._initialize_pool()
+    
+    def _initialize_pool(self):
+        """初始化连接池"""
+        for _ in range(self.max_connections):
+            conn = sqlite3.connect(self.database_path, check_same_thread=False)
+            conn.row_factory = sqlite3.Row  # 允许按列名访问
+            self.pool.put(conn)
+    
+    @contextmanager
+    def get_connection(self):
+        """获取数据库连接的上下文管理器"""
+        conn = None
+        try:
+            conn = self.pool.get(timeout=5)  # 5秒超时
+            yield conn
+        except Empty:
+            raise Exception("无法获取数据库连接：连接池已满")
+        finally:
+            if conn:
+                self.pool.put(conn)
+    
+    def close_all(self):
+        """关闭所有连接"""
+        while not self.pool.empty():
+            try:
+                conn = self.pool.get_nowait()
+                conn.close()
+            except Empty:
+                break
+
+# 全局连接池实例
+_pool = None
+_pool_lock = threading.Lock()
+
+def get_pool():
+    """获取全局连接池实例"""
+    global _pool
+    if _pool is None:
+        with _pool_lock:
+            if _pool is None:
+                conf = app_conf.conf()
+                database_path = conf.get("database", "path")
+                _pool = ConnectionPool(database_path)
+    return _pool
+
+def get_connection():
+    """获取数据库连接"""
+    return get_pool().get_connection()