fix: close panics and races the audit's own fixes left nearby

Second-pass review of the 54-commit self-correcting audit. Each item below
was confirmed by reading the surrounding source (and, where practical, the
pre-fix code) before being changed; regression tests are included for every
behavioral fix.

Concurrency:
- eventbus: Bus.Subscribe called wg.Add with no synchronization against a
  concurrent Bus.Stop's wg.Wait, a real "WaitGroup misuse" panic risk (e.g. a
  Telegram-bot settings save racing panel shutdown/restart). Stop now flips a
  mu-guarded `stopped` flag before waiting, and Subscribe checks it under the
  same lock, so Add and Wait can no longer race.

Security:
- login_limiter: evictForRoom's fallback eviction picked an arbitrary map
  key, including ones still under an active cooldown - an attacker flooding
  /login with fresh usernames could evict their own (or anyone's) blocked
  record and reset the lockout. The fallback now skips actively-blocked
  records, only falling back to an unconditional evict if the map is
  somehow entirely full of active blocks (preserves the hard memory cap).

Subscription-endpoint panics (reachable by any client hitting /sub):
- internal/sub/service.go: applyPathAndHostParams/Obj (ws/httpupgrade/xhttp
  with no path settings object) and the TLS alpn readers in three places
  used unchecked type assertions - exactly the bug class abab7cd0 patched
  elsewhere in the same switch statements, just not these call sites.
- internal/sub/json_service.go, clash_service.go: the externalProxy loops
  in the JSON and Clash generators used unchecked assertions on a
  legacy/admin-supplied field (missing "port", non-object entry, etc.).
- internal/sub/json_service.go: realityData's shortId/serverName selection
  could assert a non-string array element.

Other correctness:
- client_traffic.go: ResetAllTraffics (touched by 3eb214d0) still skipped
  clearing NodeClientTraffic node-sync baselines, unlike its sibling reset
  paths in the same file - a node's next sync would re-add pre-reset delta
  on top of the freshly-zeroed counter.
- inbound_traffic.go: the traffic-tick tx's Commit/Rollback errors were
  silently discarded; now logged so a backend-level commit failure (e.g. an
  aborted Postgres tx from a best-effort helper) doesn't masquerade as a
  successful tick.
- outbound_subscription.go: the new subscriptionFetchClient doc comment was
  wedged between fetchAndStore's existing comment and fetchAndStore itself,
  leaving fetchAndStore undocumented and the comment describing the wrong
  function.

Convention cleanup:
- Removed narrative // comments added by the audit that violate this repo's
  no-inline-comment rule (mostly narrating the specific bug/fix rather than
  a lasting contract, and mostly on new Test functions, which this repo's
  existing tests never comment) - calibrated against this exact codebase's
  own pre-existing comment style so legitimate godoc-style doc comments
  were left alone.

frontend/src/pages/clients/ClientFormModal.tsx

@@ -151,11 +151,6 @@ export function gbToBytes(gb: number): number {
   return Math.round(gb * 1024 * 1024 * 1024);
 }
 
-// The quota field displays whole/2-decimal GB, so a byte total that isn't
-// aligned to 0.01 GB (e.g. one set via the API or an import) would drift on a
-// save that never touched the field. Keep the original byte total when the
-// displayed GB still matches it, and only re-derive from GB when the user
-// actually changed the value.
 export function resolveTotalBytes(originalBytes: number | null | undefined, displayedGB: number): number {
   if (originalBytes != null && displayedGB === bytesToGB(originalBytes)) {
     return originalBytes;

frontend/src/test/outbound-link-parser.test.ts

@@ -252,8 +252,6 @@ describe('parseShadowsocksLink', () => {
   });
 
   it('decodes URL-safe base64 userinfo (as the emitter writes it)', () => {
-    // genShadowsocksLink emits Base64.encode(method:password, true) — URL-safe,
-    // so a password whose encoding contains - or _ must still round-trip.
     const method = 'aes-256-gcm';
     const password = '>>>';
     const userinfo = Base64.encode(`${method}:${password}`, true);