Add invite request system and Gitea Actions CI/CD pipeline

Invite request feature:
- Public form to request an invite when INVITE_REQUEST_ENABLED=true
- Stores requests in new invite_requests DB table
- Emails admins on new request, emails requester on approve/deny
- Admin panel tab to review, approve, and deny requests
- Approval auto-creates invite code and sends signup link

CI/CD pipeline:
- Build & push Docker image to Gitea registry on release
- Auto-deploy to staging with health check
- Manual workflow_dispatch for production deploys

Also includes client layout/sizing improvements for card grid
and opponent spacing.

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

.gitea/workflows/deploy-prod.yml

@@ -0,0 +1,51 @@
+name: Deploy Production
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Release tag to deploy (e.g. v3.3.0)'
+        required: true
+
+env:
+  IMAGE: git.adlee.work/alee/golfgame
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Deploy to production
+        uses: appleboy/ssh-action@v1
+        with:
+          host: ${{ secrets.PROD_HOST }}
+          username: root
+          key: ${{ secrets.DEPLOY_SSH_KEY }}
+          envs: IMAGE
+          script: |
+            cd /opt/golfgame
+
+            # Pull the same image that passed staging
+            docker login git.adlee.work -u ${{ secrets.REGISTRY_USER }} -p ${{ secrets.REGISTRY_TOKEN }}
+            docker pull $IMAGE:${{ github.event.inputs.tag }}
+
+            # Tag it so compose uses it
+            docker tag $IMAGE:${{ github.event.inputs.tag }} golfgame-app:latest
+
+            # Update code (for compose file / env changes)
+            git fetch origin && git checkout ${{ github.event.inputs.tag }}
+
+            # Restart app
+            docker compose -f docker-compose.prod.yml up -d app
+
+            # Wait for healthy
+            echo "Waiting for health check..."
+            for i in $(seq 1 30); do
+              if docker compose -f docker-compose.prod.yml ps app | grep -q "healthy"; then
+                echo "Production deploy successful — ${{ github.event.inputs.tag }}"
+                exit 0
+              fi
+              sleep 2
+            done
+            echo "CRITICAL: app not healthy after 60s"
+            docker compose -f docker-compose.prod.yml logs --tail=30 app
+            exit 1