Add SQLite backend for managing OpenIndexMap drafts and metadata

[srappel]

Integrate SQLite as an optional backend for storing and retrieving OpenIndexMap records and metadata.

Tasks:

• Complete basic CRUD operations:
  • Add: insert_openindexmap()
  • Get: get_openindexmap(name)
  • Update: update_openindexmap(name, json_data, metadata)
  • Delete: delete_openindexmap(name)
• Consider helper functions for:
  • Listing all stored maps
  • Exporting to GeoJSON
  • Searching by name or ID
• Optional: expose via CLI (e.g. oim db add, oim db list)
• Store location in config (e.g. config.yml)