feat(api): 支持自动实时数据源回退

- 聊天和服务号接口新增 source=auto，优先读取 WCDB realtime
- realtime 不可用时自动回退 decrypted 快照数据源
- 服务号实时读取兼容 Name2Id 字段差异和 BLOB 内容
- 实时自动同步改为可选兼容能力，补充 source=auto 回归测试

Author: 2977094657

src/wechat_decrypt_tool/chat_helpers.py

@@ -23,7 +23,6 @@
 
 logger = get_logger(__name__)
 
-_OUTPUT_DATABASES_DIR = get_output_databases_dir()
 _DEBUG_SESSIONS = os.environ.get("WECHAT_TOOL_DEBUG_SESSIONS", "0") == "1"
 _SQLITE_HEADER = b"SQLite format 3\x00"
 
@@ -33,11 +32,12 @@ def _is_valid_decrypted_sqlite(path: Path) -> bool:
 
 
 def _list_decrypted_accounts() -> list[str]:
-    if not _OUTPUT_DATABASES_DIR.exists():
+    output_databases_dir = get_output_databases_dir()
+    if not output_databases_dir.exists():
         return []
 
     accounts: list[str] = []
-    for p in _OUTPUT_DATABASES_DIR.iterdir():
+    for p in output_databases_dir.iterdir():
         if not p.is_dir():
             continue
         if _is_valid_decrypted_sqlite(p / "session.db") and _is_valid_decrypted_sqlite(p / "contact.db"):
@@ -58,8 +58,9 @@ def _resolve_account_dir(account: Optional[str]) -> Path:
     selected = str(account or "").strip() or accounts[0]
     if selected not in accounts:
         raise HTTPException(status_code=404, detail="Account not found.")
-    base = _OUTPUT_DATABASES_DIR.resolve()
-    candidate = (_OUTPUT_DATABASES_DIR / selected).resolve()
+    output_databases_dir = get_output_databases_dir()
+    base = output_databases_dir.resolve()
+    candidate = (output_databases_dir / selected).resolve()
 
     if candidate != base and base not in candidate.parents:
         raise HTTPException(status_code=400, detail="Invalid account path.")

src/wechat_decrypt_tool/chat_realtime_autosync.py

@@ -1,10 +1,10 @@
-"""Background auto-sync from WCDB realtime (db_storage) into decrypted sqlite.
+"""Optional background auto-sync from WCDB realtime (db_storage) into decrypted sqlite.
 
 Why:
-- The UI can read "latest" messages from WCDB realtime (`source=realtime`), but most APIs default to the
-  decrypted sqlite snapshot (`source=decrypted`).
-- Previously we only synced realtime -> decrypted when the UI toggled realtime off, which caused `/api/chat/messages`
-  to lag behind while realtime was enabled.
+- The chat UI now defaults to reading from WCDB realtime (`source=auto`), so it does not need a second
+  always-updated decrypted copy for display.
+- This service is kept as an opt-in compatibility bridge for workflows that still require the decrypted
+  sqlite snapshot to be incrementally updated.
 
 This module runs a lightweight background poller that watches db_storage mtime changes and triggers an incremental
 sync_all into decrypted sqlite. It is intentionally conservative (debounced + rate-limited) to avoid hammering the
@@ -105,7 +105,7 @@ class _AccountState:
 
 class ChatRealtimeAutoSyncService:
     def __init__(self) -> None:
-        self._enabled = _env_bool("WECHAT_TOOL_REALTIME_AUTOSYNC", True)
+        self._enabled = _env_bool("WECHAT_TOOL_REALTIME_AUTOSYNC", False)
         self._interval_ms = _env_int("WECHAT_TOOL_REALTIME_AUTOSYNC_INTERVAL_MS", 1000, min_v=200, max_v=10_000)
         self._debounce_ms = _env_int("WECHAT_TOOL_REALTIME_AUTOSYNC_DEBOUNCE_MS", 600, min_v=0, max_v=10_000)
         self._min_sync_interval_ms = _env_int(
@@ -181,7 +181,7 @@ def resume_account(self, account: str, reason: str = "") -> int:
 
     def start(self) -> None:
         if not self._enabled:
-            logger.info("[realtime-autosync] disabled by env WECHAT_TOOL_REALTIME_AUTOSYNC=0")
+            logger.info("[realtime-autosync] disabled (set WECHAT_TOOL_REALTIME_AUTOSYNC=1 to enable)")
             return
 
         with self._mu: