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

.gitignore

@@ -0,0 +1,16 @@
+# Environment files
+.env
+.env.*
+!.env.example
+
+# Docker volumes (large runtime data)
+volumes/
+
+# Backup files
+*.bak
+*.bak.*
+backups/
+
+# Logs
+logs/
+*.log