chore: initial project setup with backend, frontend, Android app, and CI/CD

Add complete NexaMFA push MFA system with:
- FastAPI backend with PostgreSQL, Redis, OIDC provider, and Prometheus metrics
- React TypeScript admin console
- Android Kotlin/Jetpack Compose app with biometric authentication
- Docker Compose deployment configuration
- Gitea CI workflow for backend, frontend, and Android builds
- Environment configuration template with security settings
- Documentation for security model, deployment

frontend/Dockerfile

@@ -0,0 +1,12 @@
+FROM node:22-alpine AS build
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm install
+COPY . .
+RUN npm run build
+
+FROM nginx:1.27-alpine
+COPY --from=build /app/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 CMD wget -qO- http://localhost/ || exit 1