feat(feedback): in-app user feedback with admin review and account roles

User-facing Feedback screen (Settings -> Info, registered accounts only): a
message (<=1024 runes) plus one optional attachment, an anti-spam gate (one
unreviewed message at a time), and the operator's inline reply with a
Settings/Info badge. Server-rendered admin console section (/_gm/feedback):
unread/read/archived queue with per-user search, detail with read/reply/
archive/delete/delete-all, safe attachment serving (nosniff, images inline via
<img>, others download-only). Introduces account_roles, the first per-account
role table; feedback_banned blocks only feedback submission, granted/revoked
from /users and the delete-with-block action.

- migration 00004_feedback (feedback_messages + account_roles) + jetgen
- backend internal/feedback (store+service), internal/account/roles.go
- wire: FlatBuffers feedback.submit/get/unread; gateway guest gate (Op.NonGuest,
  is_guest via session resolve) -> guest_forbidden before any backend call
- reply push reuses NotificationEvent with a new admin_reply sub-kind
- UI: /feedback route + screen, attachment picker, badge, channel detection, i18n
- tests: feedback unit (Go+UI), gateway guest-gate, inttest lifecycle, e2e
- docs: PLAN stage 19, ARCHITECTURE s15, FUNCTIONAL(+ru), TESTING, READMEs

ui/src/App.svelte

@@ -13,6 +13,7 @@
   import Stats from './screens/Stats.svelte';
   import Game from './game/Game.svelte';
   import CommsHub from './game/CommsHub.svelte';
+  import Feedback from './screens/Feedback.svelte';
   import Blocked from './screens/Blocked.svelte';
 
   onMount(() => {
@@ -26,8 +27,9 @@
     if (!insideTelegram()) return;
     const r = router.route;
     // The chat / check sub-screens step back to their game; every other sub-screen to the lobby.
-    const sub = r.name === 'gameChat' || r.name === 'gameCheck';
-    const target = sub ? `/game/${r.params.id}` : '/';
+    let target = '/';
+    if (r.name === 'gameChat' || r.name === 'gameCheck') target = `/game/${r.params.id}`;
+    else if (r.name === 'feedback') target = '/about'; // back to the Settings → Info tab
     telegramBackButton(r.name !== 'lobby' && r.name !== 'login', () => navigate(target));
   });
 
@@ -40,7 +42,7 @@
   // back-to-the-game the wrong way. dir is read with the previous depth (the effect updates it
   // only after the transition has captured its sign).
   function routeDepth(name: RouteName): number {
-    if (name === 'gameChat' || name === 'gameCheck') return 2;
+    if (name === 'gameChat' || name === 'gameCheck' || name === 'feedback') return 2;
     if (name === 'lobby' || name === 'login') return 0;
     return 1;
   }
@@ -93,6 +95,8 @@
           <SettingsHub initialTab="about" />
         {:else if router.route.name === 'friends'}
           <SettingsHub initialTab="friends" />
+        {:else if router.route.name === 'feedback'}
+          <Feedback />
         {:else if router.route.name === 'stats'}
           <Stats />
         {:else}