feat: add Docker deployment support and fix /users/me endpoint

- Add docker/ directory with Dockerfile for backend and frontend
- Backend: pytorch/pytorch CUDA base image with all qwen_tts deps
- Frontend: multi-stage nginx build with /api/ proxy to backend
- docker-compose.yml (CPU) + docker-compose.gpu.yml (GPU overlay)
- Fix /users/me returning 404 due to missing route (was caught by /{user_id})
- Update .gitignore to exclude docker/models, docker/data, docker/.env
- Update README and README.zh.md with Docker deployment instructions

Images: bdim404/qwen3-tts-backend, bdim404/qwen3-tts-frontend

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

docker/frontend/nginx.conf

@@ -0,0 +1,25 @@
+server {
+    listen 80;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    gzip on;
+    gzip_types text/plain text/css application/json application/javascript text/xml application/xml text/javascript;
+
+    location /api/ {
+        proxy_pass http://backend:8000/;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_read_timeout 300s;
+        proxy_send_timeout 300s;
+        client_max_body_size 50m;
+    }
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}