chore: clean up repo and fix docker compose configuration

- Remove outdated docs (COMPOSE.md, DOCKER.md, QUICKSTART.md, REBUILD_GUIDE.md)
- Remove build.sh, compose.production.yml, gamification-schema.sql, directus.yaml
- Simplify compose.yml for local dev (remove env var indirection)
- Add directus.yml schema snapshot and schema.sql from VPS
- Add schema:export and schema:import scripts to package.json
- Ignore .env files (vars set via compose environment)

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

packages/frontend/.env

@@ -1,4 +0,0 @@
-PUBLIC_API_URL=https://sexy.pivoine.art/api
-PUBLIC_URL=https://sexy.pivoine.art
-PUBLIC_UMAMI_ID=
-PUBLIC_UMAMI_SCRIPT=