fix: apply security and correctness review findings across both stacks

Legacy panel:
- upstream body reads now carry their own deadline and a 10 MB byte budget;
  a stalled modem can no longer hang /api/status fan-out forever nor OOM
  the proxy (request headers alone had the timeout, bodies had none)
- add X-Frame-Options DENY / CSP frame-ancestors none / nosniff; the panel
  (delete-instance and confirmed-write dialogs) is no longer clickjackable
- only send a JSON content-type when the API console request has a body, so
  payload-less dangerous writes stop failing with 400 and burning the
  one-use confirmation token
- register a form-urlencoded parser (the proxy branch was unreachable) and
  drop the multipart parser that buffered up to 60 MB before rejecting;
  bodyLimit drops to 2 MB; framework-level 415 keeps the stable error body
- remove /api/sms/send from readable paths: GET bypassed the write
  confirmation for a send endpoint
- /api/instances/:id/login maps upstream failures to a stable 502 instead
  of leaking raw error text
- guard MULTI_SIMADMIN_TIMEOUT_MS parsing (NaN aborted every request);
  prune dead code (buildClients, cookie expando no-op)

Control plane:
- deleting a notification channel detaches it from rules instead of leaving
  dangling ids that made every referencing rule unreadable and silently
  dropped future notifications; rule reads tolerate unknown ids
- startup sweep resets notification_queue rows stranded in 'sending' by a
  crash (mirrors the sms outbox sweep); terminal outbox rows are pruned on
  the retention timer
- /api/v1/metrics no longer emits operator-assigned node names on the
  session-free scrape; login limiter map is bounded and pruned; Secure
  cookie honors the gateway-declared x-forwarded-proto
- webhook delivery sets redirect: manual (signed payloads are not replayed)
- SMTP envelope sender is validated against CR/LF smuggling
- scheduled reboots with delaySeconds != 3 fail fast at the dispatcher with
  a clear reason instead of burning every retry; contract narrowed to the
  pinned baseline

apps/api/src/application/observability/metrics-service.ts

@@ -77,9 +77,9 @@ export class MetricsService {
       ]),
     );
 
-    const info = nodes.map(
-      (node) => `${PREFIX}_node_info{node="${label(node.id)}",name="${label(node.name)}"} 1`,
-    );
+    // Operator-assigned names can leak hostnames/locations to unauthenticated
+    // scrapers; the series intentionally stays opaque to node ids.
+    const info = nodes.map((node) => `${PREFIX}_node_info{node="${label(node.id)}"} 1`);
     lines.push(
       ...sample(`${PREFIX}_node_info`, 'Registered nodes and their addresses.', 'gauge', info),
       ...sample(`${PREFIX}_nodes_total`, 'Number of registered nodes.', 'gauge', [