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>

.github/workflows/ci.yml

@@ -61,7 +61,6 @@ jobs:
       clock-web: ${{ steps.changes.outputs.clock-web }}
       contacts-backend: ${{ steps.changes.outputs.contacts-backend }}
       contacts-web: ${{ steps.changes.outputs.contacts-web }}
-      presi-backend: ${{ steps.changes.outputs.presi-backend }}
       presi-web: ${{ steps.changes.outputs.presi-web }}
       storage-backend: ${{ steps.changes.outputs.storage-backend }}
       storage-web: ${{ steps.changes.outputs.storage-web }}
@@ -96,7 +95,6 @@ jobs:
             echo "clock-web=true" >> $GITHUB_OUTPUT
             echo "contacts-backend=true" >> $GITHUB_OUTPUT
             echo "contacts-web=true" >> $GITHUB_OUTPUT
-            echo "presi-backend=true" >> $GITHUB_OUTPUT
             echo "presi-web=true" >> $GITHUB_OUTPUT
             echo "storage-backend=true" >> $GITHUB_OUTPUT
             echo "storage-web=true" >> $GITHUB_OUTPUT
@@ -135,7 +133,6 @@ jobs:
             echo "clock-web=true" >> $GITHUB_OUTPUT
             echo "contacts-backend=true" >> $GITHUB_OUTPUT
             echo "contacts-web=true" >> $GITHUB_OUTPUT
-            echo "presi-backend=true" >> $GITHUB_OUTPUT
             echo "presi-web=true" >> $GITHUB_OUTPUT
             echo "storage-backend=true" >> $GITHUB_OUTPUT
             echo "storage-web=true" >> $GITHUB_OUTPUT
@@ -275,13 +272,7 @@ jobs:
             echo "contacts-web=false" >> $GITHUB_OUTPUT
           fi
 
-          # presi-backend
-          PRESI_BACKEND_CHANGED=$(check_pattern "apps/presi/apps/backend/|apps/presi/packages/")
-          if [ "$COMMON_CHANGED" == "true" ] || [ "$SHARED_AUTH_CHANGED" == "true" ] || [ "$PRESI_BACKEND_CHANGED" == "true" ]; then
-            echo "presi-backend=true" >> $GITHUB_OUTPUT
-          else
-            echo "presi-backend=false" >> $GITHUB_OUTPUT
-          fi
+          # presi-backend: REMOVED — replaced by Hono server
 
           # presi-web
           PRESI_WEB_CHANGED=$(check_pattern "apps/presi/apps/web/|apps/presi/packages/")
@@ -383,7 +374,7 @@ jobs:
           echo "| clock-web | ${{ steps.changes.outputs.clock-web }} |" >> $GITHUB_STEP_SUMMARY
           echo "| contacts-backend | ${{ steps.changes.outputs.contacts-backend }} |" >> $GITHUB_STEP_SUMMARY
           echo "| contacts-web | ${{ steps.changes.outputs.contacts-web }} |" >> $GITHUB_STEP_SUMMARY
-          echo "| presi-backend | ${{ steps.changes.outputs.presi-backend }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| presi-backend | removed |" >> $GITHUB_STEP_SUMMARY
           echo "| presi-web | ${{ steps.changes.outputs.presi-web }} |" >> $GITHUB_STEP_SUMMARY
           echo "| storage-backend | ${{ steps.changes.outputs.storage-backend }} |" >> $GITHUB_STEP_SUMMARY
           echo "| storage-web | ${{ steps.changes.outputs.storage-web }} |" >> $GITHUB_STEP_SUMMARY
@@ -808,34 +799,7 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
 
-  build-presi-backend:
-    name: Build presi-backend
-    runs-on: ubuntu-latest
-    needs: detect-changes
-    if: needs.detect-changes.outputs.presi-backend == 'true'
-    steps:
-      - uses: actions/checkout@v4
-      - uses: docker/setup-qemu-action@v3
-      - uses: docker/setup-buildx-action@v3
-      - uses: docker/login-action@v3
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-      - uses: docker/metadata-action@v5
-        id: meta
-        with:
-          images: ghcr.io/${{ github.repository_owner }}/presi-backend
-          tags: type=raw,value=latest
-      - uses: docker/build-push-action@v5
-        with:
-          context: .
-          file: apps/presi/apps/backend/Dockerfile
-          platforms: linux/amd64,linux/arm64
-          push: true
-          tags: ${{ steps.meta.outputs.tags }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+  # build-presi-backend: REMOVED — replaced by Hono server
 
   build-presi-web:
     name: Build presi-web