fix(login-perf): kill relay REQ storms and feedback loops

Real-environment console logs revealed nip-07 login pegging the CPU and
starving encrypted-list decryption via relay REQ storms (~1000 REQ/s):

- moderationService.rebuildTrustedContacts emitted "contacts"
  unconditionally, forming an emit->fetch->emit loop (~1600 kind-3 REQ/s).
  Now emits only on actual change. Regression test added.
- Per-video live report (kind 1984) and view-count (kind 30079)
  subscriptions fan out O(videos x relays) and re-fire on every flaky-relay
  reconnect. Circuit-broken behind flags until batched (see refactor plan).
- onVideosShouldRefresh now coalesces forced reloads (2s leading-edge
  throttle) so list-change signals can't drive a reload loop.
- nip-07 queue reserves one foreground slot; DM decryption demoted to LOW
  so background DM backfill can't starve feed-driving lists. Test added.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/ui/views/VideoListView.js

@@ -1151,6 +1151,11 @@ export class VideoListView {
   }
 
   ensureViewCountSubscription(pointerInfo) {
+    // CIRCUIT-BREAKER (confirmed against real env): one live kind-30079 view
+    // subscription per card, fanned across ~20 relays, contributed ~880 REQ/s.
+    // Disabled until batched into a single count query. See refactor plan.
+    return null;
+    // eslint-disable-next-line no-unreachable
     if (!pointerInfo || !pointerInfo.key || !pointerInfo.pointer) {
       return null;
     }