Feat: Register non-spatial GeoPackage tables in gpkg_contents

[Copilot]

Description

GeoPackage consumers expect all tables (including non-spatial) to be discoverable via gpkg_contents; currently only spatial tables are registered. This PR adds spec-aligned handling for non-spatial tables so they are created as attributes entries and removed cleanly on drop.

• Dialect behavior updates

  • after_create now inserts a gpkg_contents row for tables without geometry columns:
    • data_type = 'attributes'
    • srs_id = 0
  • before_drop now removes the corresponding gpkg_contents row for non-spatial tables.

• Focused regression coverage

  • Added unit tests for GeoPackage admin hooks to verify:
    • non-spatial table registration on create
    • non-spatial table cleanup on drop

if not is_spatial:
    bind.execute(
        text(
            """INSERT INTO gpkg_contents VALUES (
                :table_name, 'attributes', :table_name, "",
                strftime('%Y-%m-%dT%H:%M:%fZ', CURRENT_TIMESTAMP),
                NULL, NULL, NULL, NULL, 0
            );"""
        ).bindparams(table_name=table.name)
    )

Checklist

This pull request is:

• A documentation / typographical error fix
  • Good to go, no issue or tests are needed
• A short code fix
  • Please include tests that fail with the main branch and pass with the provided fix.
• A new feature implementation or update an existing feature
  • Please include tests that cover every lines of the new/updated feature.
  • Please update the documentation to describe the new/updated feature.