refactor(presi): replace NestJS backend with lightweight Hono server

The Presi NestJS backend (40 source files, 50 deps) was a CRUD wrapper
around decks, slides, and themes — all now handled by local-first sync.

Only the share-link feature requires server-side state (public URLs
without auth), so a minimal Hono + Bun server replaces the entire
NestJS backend:

- apps/presi/apps/server/ — Hono server with share routes + GDPR admin
  Uses @manacore/shared-hono for auth (JWKS), health, admin, errors
- Web app API client stripped to share-only (was 270 lines → 90 lines)
- Removed from docker-compose, CI/CD, Prometheus, env generation
- NestJS backend deleted (40 TS files, 8 test specs, 3038 lines)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/setup-databases.sh

@@ -164,7 +164,7 @@ setup_service() {
             ;;
         presi)
             create_db_if_not_exists "presi"
-            push_schema "@presi/backend" "presi"
+            # Schema managed by mana-sync (NestJS backend removed, Hono server for shares)
             ;;
         storage)
             create_db_if_not_exists "storage"