Add k3s deployment: Dockerfiles, nginx config, CI pipeline

- Backend Dockerfile: multi-stage rust:1.87 → debian:bookworm-slim
- Frontend Dockerfile: multi-stage node:22-alpine → nginx:alpine
- Frontend nginx.conf: serve static + proxy /api/ to backend service
- Change API_URL to relative /api for containerized deployment
- Woodpecker CI pipeline to build and push images to Gitea Registry
- Add repository URL to CLAUDE.md

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

frontend/nginx.conf

@@ -0,0 +1,17 @@
+server {
+    listen 80;
+    server_name _;
+
+    location / {
+        root /usr/share/nginx/html;
+        index index.html;
+        try_files $uri $uri/ /index.html;
+    }
+
+    location /api/ {
+        proxy_pass http://bbb-backend.bbb.svc.cluster.local:3000;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    }
+}