feat: in-app support form with email + Gitea issue integration (v0.49.0)

Users can now report bugs, suggestions, or questions from a new /support
page. Each submission sends a confirmation email and, when GITEA_URL/
GITEA_TOKEN/GITEA_REPO are configured in admin Settings, opens a labeled
issue on that repo automatically (best-effort — failure doesn't block the
ticket). Admins get a Support section to triage status and retry failed
Gitea issue creation.

New support_tickets table, gitea.ts client, site-settings entries for the
three new secrets, and OpenAPI docs for the two user-facing endpoints.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/admin/settings/page.tsx

@@ -11,6 +11,11 @@ const SETTING_GROUPS = [
     description: "Keys for web push notifications. Generate with: npx web-push generate-vapid-keys",
     keys: ["NEXT_PUBLIC_VAPID_PUBLIC_KEY", "VAPID_PRIVATE_KEY"] as const,
   },
+  {
+    title: "Gitea Integration",
+    description: "Support tickets submitted in-app automatically open an issue on this Gitea repo. Token needs issue read/write scope on the target repo.",
+    keys: ["GITEA_URL", "GITEA_TOKEN", "GITEA_REPO"] as const,
+  },
 ];
 
 export default async function AdminSettingsPage() {