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/notifications.py

@@ -261,7 +261,10 @@ def register_notifications_tool(mcp: FastMCP) -> None:
                     "importance": importance.upper(),
                 }
                 data = await make_graphql_request(MUTATIONS["create"], {"input": input_data})
-                return {"success": True, "data": data}
+                notification = data.get("createNotification")
+                if notification is None:
+                    raise ToolError("Notification creation failed: server returned no data")
+                return {"success": True, "notification": notification}
 
             if action in ("archive", "unread"):
                 if not notification_id: