feat(logs): add connection and run-by-you filters

[DangTAnh]

Summary

The Recent Query Logs page had no filtering, so finding runs for a specific connection or your own runs meant paging through everything. This adds two query-param filters to ListQueryLogView (connection and run_by_me) plus a filter form on the logs page. No new dependencies (plain GET params instead of django-filter) and no log schema changes.

Changes

• explorer/views/list.py: ListQueryLogView filters by database_connection_id and current user, exposes filter context (connections, selection, querystring)
• explorer/templates/explorer/querylog_list.html: connection dropdown + "Run by you" checkbox form; pagination links preserve active filters
• explorer/tests/test_views.py: filter-by-connection (incl. invalid value ignored) and run-by-me tests

Testing

• manage.py test explorer.tests.test_views.TestQueryLog --settings=explorer.tests.settings_base — 8 tests OK
• manage.py test explorer --settings=explorer.tests.settings_base — 276 tests, only 2 pre-existing failures unrelated to this change (assistant history ordering and a Windows-path assertion, both fail on clean master too)

Related

Fixes #665