Fix deadlock in lazy init: _ensure_initialized calling login via request()

login() called client.request() which called _ensure_initialized() which
tried to re-acquire _init_lock — deadlocking forever. Fix: set
_initializing=True while inside the init critical section so request()
skips the _ensure_initialized() guard when called from within init
(safe because query_api_info() already populated the API cache).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mcp_synology_container/dsm_client.py

@@ -101,6 +101,7 @@ class DsmClient:
         self._reauth_lock = asyncio.Lock()
         self._init_lock = asyncio.Lock()
         self._initialized = False
+        self._initializing = False  # True while inside _ensure_initialized
         logger.debug(
             "DsmClient: base_url=%s verify_ssl=%s timeout=%d",
             self._base_url,
@@ -131,6 +132,8 @@ class DsmClient:
         async with self._init_lock:
             if self._initialized:  # re-check inside lock
                 return
+            self._initializing = True
+            try:
                 sys.stderr.write(f"[dsm] Connecting to {self._base_url}...\n")
                 sys.stderr.flush()
                 logger.debug("Lazy init: querying API info from %s", self._base_url)
@@ -146,6 +149,8 @@ class DsmClient:
                     sys.stderr.flush()
                 self._initialized = True
                 logger.debug("Lazy init complete")
+            finally:
+                self._initializing = False
 
     async def __aenter__(self) -> DsmClient:
         logging.getLogger("httpx").setLevel(logging.WARNING)
@@ -235,6 +240,9 @@ class DsmClient:
         """
         sys.stderr.write(f"[dsm] request: {api}/{method}\n")
         sys.stderr.flush()
+        # Skip init guard if we are already inside _ensure_initialized (e.g. login call).
+        # The API cache is populated before login, so the cache is ready at this point.
+        if not self._initializing:
             await self._ensure_initialized()
         http = self._get_http()