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/Dockerfile

@@ -0,0 +1,18 @@
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY qwen3-tts-frontend/package*.json ./
+RUN npm ci
+
+COPY qwen3-tts-frontend/ .
+RUN npm run build
+
+FROM nginx:alpine
+
+COPY --from=builder /app/dist /usr/share/nginx/html
+COPY docker/frontend/nginx.conf /etc/nginx/conf.d/default.conf
+
+EXPOSE 80
+
+CMD ["nginx", "-g", "daemon off;"]