feat: customer frontend, Sungrow collector fixes, real data (v1.2.0)

- Add frontend/ at root (no Three.js, no Charging, green #52c41a theme)
- Fix Sungrow collector: add curPage/size params, unit conversion
- Fix station-level dedup to prevent double-counting
- Add shared token cache for API rate limit protection
- Add .githooks/pre-commit, CLAUDE.md, .gitignore
- Update docker-compose.override.yml frontend -> ./frontend
- Pin bcrypt in requirements.txt
- Add BUYOFF_RESULTS_2026-04-05.md (39/43 pass)
- Data accuracy: 0.0% diff vs iSolarCloud

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

frontend/Dockerfile.prod

@@ -0,0 +1,20 @@
+# Multi-stage production build for standalone use
+# In docker-compose.prod.yml, the nginx Dockerfile handles frontend building directly
+
+# Stage 1: Build
+FROM node:20-alpine AS builder
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+# Stage 2: Serve with nginx
+FROM nginx:1.27-alpine
+COPY --from=builder /app/dist /usr/share/nginx/html
+
+# SPA fallback
+RUN echo 'server { listen 80; root /usr/share/nginx/html; index index.html; location / { try_files $uri $uri/ /index.html; } }' > /etc/nginx/conf.d/default.conf
+
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]