feat: add Linux support with cross-platform memory scanning

- Add Linux memory scanner (`find_all_keys_linux.py`) using `/proc/<pid>/mem`,
  same approach as Windows/macOS — no GDB, no function offsets, no restart needed
- Extract Windows-specific code to `find_all_keys_windows.py`
- Make `find_all_keys.py` a platform dispatcher (Windows / Linux)
- Add `key_utils.py` for cross-platform path matching (`/` vs `\` in all_keys.json)
- Update `config.py` with Linux auto-detection of db_storage paths
- Update all consumers (decrypt_db, monitor, monitor_web, mcp_server) to use
  `get_key_info()` for platform-agnostic key lookup

Tested on remote Linux container: 15/15 DBs scanned, decrypted, and verified.

decrypt_db.py

@@ -7,7 +7,7 @@ WeChat 4.0 数据库解密器
 """
 import hashlib, struct, os, sys, json
 import hmac as hmac_mod
-from Crypto.Cipher import AES
+from Crypto.Cipher import AES
 
 import functools
 print = functools.partial(print, flush=True)
@@ -20,11 +20,12 @@ HMAC_SZ = 64
 RESERVE_SZ = 80  # IV(16) + HMAC(64)
 SQLITE_HDR = b'SQLite format 3\x00'
 
-from config import load_config
-_cfg = load_config()
-DB_DIR = _cfg["db_dir"]
-OUT_DIR = _cfg["decrypted_dir"]
-KEYS_FILE = _cfg["keys_file"]
+from config import load_config
+from key_utils import get_key_info, strip_key_metadata
+_cfg = load_config()
+DB_DIR = _cfg["db_dir"]
+OUT_DIR = _cfg["decrypted_dir"]
+KEYS_FILE = _cfg["keys_file"]
 
 
 def derive_mac_key(enc_key, salt):
@@ -115,13 +116,13 @@ def main():
         print("请先运行 find_all_keys.py")
         sys.exit(1)
 
-    with open(KEYS_FILE) as f:
-        keys = json.load(f)
-
-    keys.pop("_db_dir", None)
-    print(f"\n加载 {len(keys)} 个数据库密钥")
-    print(f"输出目录: {OUT_DIR}")
-    os.makedirs(OUT_DIR, exist_ok=True)
+    with open(KEYS_FILE) as f:
+        keys = json.load(f)
+
+    keys = strip_key_metadata(keys)
+    print(f"\n加载 {len(keys)} 个数据库密钥")
+    print(f"输出目录: {OUT_DIR}")
+    os.makedirs(OUT_DIR, exist_ok=True)
 
     # 收集所有DB文件
     db_files = []
@@ -129,7 +130,7 @@ def main():
         for f in files:
             if f.endswith('.db') and not f.endswith('-wal') and not f.endswith('-shm'):
                 path = os.path.join(root, f)
-                rel = os.path.relpath(path, DB_DIR).replace('\\', '/')
+                rel = os.path.relpath(path, DB_DIR)
                 sz = os.path.getsize(path)
                 db_files.append((rel, path, sz))
 
@@ -141,16 +142,15 @@ def main():
     failed = 0
     total_bytes = 0
 
-    for rel, path, sz in db_files:
-        # 统一用正斜杠查找key
-        rel_key = rel.replace('\\', '/')
-        if rel_key not in keys:
-            print(f"SKIP: {rel} (无密钥)")
-            failed += 1
-            continue
-
-        enc_key = bytes.fromhex(keys[rel_key]["enc_key"])
-        out_path = os.path.join(OUT_DIR, rel)
+    for rel, path, sz in db_files:
+        key_info = get_key_info(keys, rel)
+        if not key_info:
+            print(f"SKIP: {rel} (无密钥)")
+            failed += 1
+            continue
+
+        enc_key = bytes.fromhex(key_info["enc_key"])
+        out_path = os.path.join(OUT_DIR, rel)
 
         print(f"解密: {rel} ({sz/1024/1024:.1f}MB) ...", end=" ")