Add CLAUDE.md with project info and deployment instructions

CLAUDE.md

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+# RS-UV3A
+
+Documentation site for the RS-UV3A VHF/UHF transceiver by HobbyPCB.
+
+- **Production**: https://rs-uv3a.warehack.ing
+- **Git**: `git@git.supported.systems:RF/rs-uv3a.git`
+- **Server**: `ssh -A warehack-ing@warehack.ing`, repo at `~/rs-uv3a`
+
+## Stack
+
+- Astro/Starlight (static output)
+- Docker multi-stage build (Node builder -> Caddy prod)
+- caddy-docker-proxy on external `caddy` network
+- Makefile with `include .env` for environment-driven dev/prod switching
+
+## Environment
+
+Create `.env` in project root:
+
+```env
+COMPOSE_PROJECT=rs-uv3a-docs
+DOMAIN=rs-uv3a.warehack.ing
+ENVIRONMENT=prod
+```
+
+## Commands
+
+```bash
+make up        # Start services (detached)
+make down      # Stop services
+make logs      # Follow service logs
+make prod      # Switch to prod mode and restart
+make dev       # Switch to dev mode and restart
+make rebuild   # Full rebuild (no cache)
+make status    # Show running containers
+make clean     # Remove containers, images, volumes
+make help      # Show all targets
+```
+
+## Deploy to Production
+
+```bash
+ssh -A warehack-ing@warehack.ing "cd ~/rs-uv3a && git pull && make up"
+```