ci: 增加前端构建发布流水线

新增 Gitea CI，覆盖 Android OTA 发布与校验、Android Release APK 打包，以及 Web Docker 镜像构建推送。

Made-with: Cursor

Dockerfile.web

@@ -0,0 +1,15 @@
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY package.json package-lock.json ./
+RUN npm ci
+
+COPY . .
+RUN npx expo export --platform web --output-dir dist-web
+
+FROM nginx:1.27-alpine
+
+COPY --from=builder /app/dist-web /usr/share/nginx/html
+
+EXPOSE 80