fix: address PR review critical and high findings

- Remove duplicate _cap_log_content definition (dead code merge artifact)
  from manager.py; keep byte-count version that correctly handles multibyte UTF-8
- Fix storage.py unassigned handler reading wrong key (unassignedDevices → disks)
  — query already fetched `disks {}` but handler returned empty list every call
- Add null checks to all 8 Docker organizer object mutations; raise ToolError
  instead of silently returning success=True with organizer=None
- Raise ToolError in docker logs when server returns no log data
- Extract notification object from create response (was returning raw GraphQL
  wrapper dict instead of the notification itself)
- Raise ToolError in test_subscription_query on connection failure and unexpected
  exceptions (was returning error dicts, bypassing error handling)
- Remove stale "Bug N fix" inline comments from diagnostics.py
- Update docker.py module docstring to reflect 26 actions (was 15)
- Bump version 0.4.1 → 0.4.2

Co-authored-by: Claude <claude@anthropic.com>

unraid_mcp/tools/storage.py

@@ -204,7 +204,7 @@ def register_storage_tool(mcp: FastMCP) -> None:
                 return {"summary": summary, "details": raw}
 
             if action == "unassigned":
-                return {"devices": data.get("unassignedDevices", [])}
+                return {"devices": data.get("disks", [])}
 
             if action == "log_files":
                 return {"log_files": data.get("logFiles", [])}