* fix: implement CASCADE DELETE for source deletion timeout issue
- Add migration 009 to add CASCADE DELETE constraints to foreign keys
- Simplify delete_source() to only delete parent record
- Database now handles cascading deletes efficiently
- Fixes timeout issues when deleting sources with thousands of pages
* chore: update complete_setup.sql to include CASCADE DELETE constraints
- Add ON DELETE CASCADE to foreign keys in initial setup
- Include migration 009 in the migrations tracking
- Ensures new installations have CASCADE DELETE from the start
