feat: add unified entry point and multi-process key extraction

Add main.py as single entry point that auto-detects config, extracts keys, and launches Web UI or decrypts databases in one command.
Refactor find_all_keys to scan all Weixin.exe processes instead of only the largest one, enabling multi=account support.

main.py

@@ -0,0 +1,99 @@
+"""
+WeChat Decrypt 一键启动
+
+python main.py          # 提取密钥 + 启动 Web UI
+python main.py decrypt  # 提取密钥 + 解密全部数据库
+"""
+import json
+import os
+import subprocess
+import sys
+
+import functools
+print = functools.partial(print, flush=True)
+
+
+def check_wechat_running():
+    """检查微信是否在运行，返回 True/False"""
+    r = subprocess.run(
+        ["tasklist", "/FI", "IMAGENAME eq Weixin.exe", "/FO", "CSV", "/NH"],
+        capture_output=True, text=True,
+    )
+    for line in r.stdout.strip().split("\n"):
+        if "Weixin.exe" in line:
+            return True
+    return False
+
+
+def ensure_keys(keys_file):
+    """确保密钥文件存在，不存在则自动提取"""
+    if os.path.exists(keys_file):
+        with open(keys_file) as f:
+            keys = json.load(f)
+        if keys:
+            print(f"[+] 已有 {len(keys)} 个数据库密钥")
+            return
+
+    print("[*] 密钥文件不存在，正在从微信进程提取...")
+    print()
+    from find_all_keys import main as extract_keys
+    extract_keys()
+    print()
+
+    # 提取后再次检查
+    if not os.path.exists(keys_file):
+        print("[!] 密钥提取失败")
+        sys.exit(1)
+    with open(keys_file) as f:
+        keys = json.load(f)
+    if not keys:
+        print("[!] 未能提取到任何密钥")
+        print("    可能原因：选择了错误的微信数据目录，或微信需要重启")
+        print("    请检查 config.json 中的 db_dir 是否与当前登录的微信账号匹配")
+        sys.exit(1)
+
+
+def main():
+    print("=" * 60)
+    print("  WeChat Decrypt")
+    print("=" * 60)
+    print()
+
+    # 1. 加载配置（自动检测 db_dir）
+    from config import load_config
+    cfg = load_config()
+
+    # 2. 检查微信进程
+    if not check_wechat_running():
+        print("[!] 未检测到微信进程 (Weixin.exe)")
+        print("    请先启动微信并登录，然后重新运行")
+        sys.exit(1)
+    print("[+] 微信进程运行中")
+
+    # 3. 提取密钥
+    ensure_keys(cfg["keys_file"])
+
+    # 4. 根据子命令执行
+    cmd = sys.argv[1] if len(sys.argv) > 1 else "web"
+
+    if cmd == "decrypt":
+        print("[*] 开始解密全部数据库...")
+        print()
+        from decrypt_db import main as decrypt_all
+        decrypt_all()
+    elif cmd == "web":
+        print("[*] 启动 Web UI...")
+        print()
+        from monitor_web import main as start_web
+        start_web()
+    else:
+        print(f"[!] 未知命令: {cmd}")
+        print()
+        print("用法:")
+        print("  python main.py          启动实时消息监听 (Web UI)")
+        print("  python main.py decrypt  解密全部数据库到 decrypted/")
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()