feat: migrate to docker-compose with selfhosted-supabase-mcp

- Replace legacy directory structure (api/, db/, functions/, logs/, pooler/) with
  single docker-compose.yml based self-hosted setup
- Add selfhosted-supabase-mcp TypeScript MCP server for database management
- Add .dockerignore for Docker build context
- Update .gitignore to exclude .env files, volumes/, backups, logs

.dockerignore

@@ -0,0 +1,4 @@
+volumes/db/data
+volumes/storage
+volumes/logs
+.git