fix: correct marketplace.json source field and improve async operations

- Fix marketplace.json: change source from relative path to GitHub URL
  (was "skills/unraid", now "https://github.com/jmagar/unraid-mcp")
  This resolves the "Invalid input" schema validation error when adding
  the marketplace to Claude Code

- Refactor subscriptions autostart to use anyio.Path for async file checks
  (replaces blocking pathlib.Path.exists() with async anyio.Path.exists())

- Update dependencies: anyio 4.11.0→4.12.1, attrs 25.3.0→25.4.0

unraid_mcp/subscriptions/resources.py

@@ -6,8 +6,8 @@ and the MCP protocol, providing fallback queries when subscription data is unava
 
 import json
 import os
-from pathlib import Path
 
+import anyio
 from fastmcp import FastMCP
 
 from ..config.logging import logger
@@ -50,7 +50,7 @@ async def autostart_subscriptions() -> None:
     if log_path is None:
         # Default to syslog if available
         default_path = "/var/log/syslog"
-        if Path(default_path).exists():
+        if await anyio.Path(default_path).exists():
             log_path = default_path
             logger.info(f"[AUTOSTART] Using default log path: {default_path}")