fix(beszel): address review findings for live streaming

- Skip toReversed() for live data (already chronological from buffer)
- Reset live buffer on systemId/integration change to avoid stale data
- Throw on unexpected SSE stream end so subscription emits error
- Delete unused time-period.ts config (duplicate of server-side config)

packages/integrations/src/beszel/beszel-integration.ts

@@ -329,6 +329,9 @@ export class BeszelIntegration extends Integration {
           processLine(line);
         }
       }
+      if (!signal.aborted) {
+        throw new Error("Beszel SSE stream ended unexpectedly");
+      }
     } finally {
       reader.cancel().catch(() => {});
     }