chore: remove the bug-report integration

Drop the in-app bug-report surface end to end: the user submission page,
the feedback intake and admin inbox, the optional GitHub-issue
escalation, the operator config, and the dedicated achievement badges.

- delete the /bugreport page and the bugreport / feedback / admin-feedback API routes
- drop the Feedback model, its enums, and the AppSettings GitHub-issue and enable columns (migration 0205)
- remove the admin Feedback section, the Bug Report integration card, and the system-status row
- drop the bug-report nav entry and the app-settings provider that only carried its flag
- remove the bug-hunter achievement badges and their metric
- prune the related i18n keys across every locale and the encrypted-column and key-rotation registries

src/components/admin/admin-shell.tsx

@@ -23,7 +23,6 @@ import {
   FileText,
   Info,
   KeyRound,
-  Inbox,
   Plug,
   Radio,
   ScrollText,
@@ -89,11 +88,6 @@ export const ADMIN_SECTIONS: readonly AdminSection[] = [
     titleKey: "admin.section.module-availability.title",
     icon: Blocks,
   },
-  {
-    slug: "feedback",
-    titleKey: "admin.section.feedback.title",
-    icon: Inbox,
-  },
   {
     slug: "reminders",
     titleKey: "admin.section.reminders.title",