fix: serve static files in production

- Added static file serving in Express for production
- Added SPA fallback for client-side routing
- Created Dockerfile with NODE_ENV=production
- Frontend now properly served at dash.descomplicar.pt

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,25 @@
+FROM node:22-alpine
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+
+# Install ALL dependencies (needed for build)
+RUN npm ci
+
+# Copy source
+COPY . .
+
+# Build frontend and API
+RUN npm run build
+
+# Set production environment
+ENV NODE_ENV=production
+ENV API_PORT=3001
+
+# Expose port
+EXPOSE 3001
+
+# Start command (serves API + static frontend)
+CMD ["npm", "start"]