feat(ui): add Adaptive Prompt Tuner tab with correction submission UI

- Add pgCorrectedModerationsTable to shared schema
- Create backend corrections module (stats, list, create endpoints)
- Add TunerPanel with Stats, History, and Submit sub-tabs
- Add AuthOverlay gate for Tuner (admin-only, same as Live)
- Set messages as default tab
- Wire Tuner into sidebar, header, and mobile tab bar

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

services/frontend/src/widgets/Header.tsx

@@ -10,11 +10,13 @@ import type { WsStatus } from "../shared/ws/socket";
 const titles: Record<DashboardTab, string> = {
   live: "Voice, Media & Recordings",
   messages: "Messages & Moderation",
+  tuner: "Prompt Tuner",
 };
 
 const subtitles: Record<DashboardTab, string> = {
   live: "Join voice channels, play media, stream audio, and browse recordings.",
   messages: "Capture, analyse, and moderate Discord messages.",
+  tuner: "Monitor correction patterns and improve AI moderation accuracy.",
 };
 
 interface HeaderProps {