fix(beszel): improve live subscription error handling and cleanup

- Surface subscription errors in useLiveStats via onError + error state
- Show error UI in live mode when SSE connection fails
- Abort SSE reader on subscribeTopic failure instead of silent log
- Guard mock realtime against pre-aborted signal to prevent interval leak
- Remove dead includeDocker from subscription input schema

packages/api/src/router/widgets/beszel.ts

@@ -154,7 +154,6 @@ export const beszelRouter = createTRPCRouter({
     .input(
       z.object({
         systemId: z.string(),
-        includeDocker: z.boolean().default(true),
       }),
     )
     .subscription(({ ctx, input }) => {