Add landing page, Docker setup, and CI/CD pipeline

React + Vite + TypeScript + Tailwind frontend with landing page,
Docker Compose for dev and prod (nginx-proxy integration),
and Gitea Actions workflow for automated deployment.

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

frontend/Dockerfile.prod

@@ -0,0 +1,14 @@
+# Stage 1: Build
+FROM node:20-slim AS build
+RUN corepack enable && corepack prepare pnpm@latest --activate
+WORKDIR /app
+COPY package.json pnpm-lock.yaml ./
+RUN pnpm install --frozen-lockfile
+COPY . .
+RUN pnpm run build
+
+# Stage 2: Serve
+FROM nginx:alpine
+COPY --from=build /app/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80