v0.3.0: structural refactor — go:embed templates, server split, domain rename

- Migrate all 7 HTML templates + CSS from Go string constants to individual
  go:embed files in internal/web/templates/ (templates.go: 2150→35 lines)
- Split server.go into auth.go, handlers.go, funcmap.go (server.go: 540→120 lines)
- Rename controller subdomain from dashboard.* to felhom.* in Traefik labels
- Update documentation (CLAUDE.md, README.md, CONTEXT.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

controller/docker-compose.yml

@@ -29,7 +29,7 @@ services:
       - TZ=Europe/Budapest
     labels:
       - "traefik.enable=true"
-      - "traefik.http.routers.controller.rule=Host(`dashboard.${DOMAIN}`)"
+      - "traefik.http.routers.controller.rule=Host(`felhom.${DOMAIN}`)"
       - "traefik.http.routers.controller.entrypoints=websecure"
       - "traefik.http.routers.controller.tls=true"
       - "traefik.http.services.controller.loadbalancer.server.port=8080"