feat: add Docker deployment configuration

Add backend and frontend Dockerfiles, docker-compose setup with nginx
reverse proxy, .dockerignore files and Makefile for dev/prod workflows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/nginx.conf

@@ -0,0 +1,19 @@
+server {
+    listen 80;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Proxy API requests to backend
+    location /api {
+        proxy_pass http://backend:8000;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        client_max_body_size 50M;
+    }
+
+    # SPA fallback
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}