Fix Claude Desktop loading: lazy NAS connection on first tool call

Previously the server blocked at startup waiting for query_api_info()
and login() before starting the MCP protocol. Claude Desktop has a short
initialization timeout and dropped the server before the handshake started.

Changes:
- DsmClient: add _ensure_initialized() with asyncio.Lock for thread-safe
  lazy init; called automatically at the start of request(), upload_text(),
  and download_text() on the first use.
- cli.py serve: remove upfront query_api_info() and auth.login() calls;
  the server now starts immediately ("MCP server ready" on stderr) and
  connects to the NAS on the first tool invocation.

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

src/mcp_synology_container/dsm_client.py

@@ -98,6 +98,8 @@ class DsmClient:
         self._sid: str | None = None
         self._auth_manager: AuthManager | None = None
         self._reauth_lock = asyncio.Lock()
+        self._init_lock = asyncio.Lock()
+        self._initialized = False
         logger.debug(
             "DsmClient: base_url=%s verify_ssl=%s timeout=%d",
             self._base_url,
@@ -118,6 +120,24 @@ class DsmClient:
         """Register the AuthManager for automatic re-login on session errors."""
         self._auth_manager = auth_manager
 
+    async def _ensure_initialized(self) -> None:
+        """Connect to NAS and authenticate on first use (lazy init).
+
+        Subsequent calls are no-ops. Thread-safe via asyncio.Lock.
+        """
+        if self._initialized:
+            return
+        async with self._init_lock:
+            if self._initialized:  # re-check inside lock
+                return
+            logger.debug("Lazy init: querying API info from %s", self._base_url)
+            await self.query_api_info()
+            if self._auth_manager:
+                logger.debug("Lazy init: authenticating")
+                self._sid = await self._auth_manager.login(self)
+            self._initialized = True
+            logger.debug("Lazy init complete")
+
     async def __aenter__(self) -> DsmClient:
         logging.getLogger("httpx").setLevel(logging.WARNING)
         logging.getLogger("httpcore").setLevel(logging.WARNING)
@@ -204,6 +224,7 @@ class DsmClient:
         Raises:
             SynologyError: On API errors.
         """
+        await self._ensure_initialized()
         http = self._get_http()
 
         if api not in self._api_cache:
@@ -278,6 +299,7 @@ class DsmClient:
             Response data dict.
         """
         api = "SYNO.FileStation.Upload"
+        await self._ensure_initialized()
         http = self._get_http()
 
         if api not in self._api_cache:
@@ -328,6 +350,7 @@ class DsmClient:
             File content as string.
         """
         api = "SYNO.FileStation.Download"
+        await self._ensure_initialized()
         http = self._get_http()
 
         if api not in self._api_cache: