v0.20.36

Added

• Migration v10: new ics_subscriptions table with fields for name, URL, color, shared flag, created_by, etag, last_modified, last_sync, and created_at
• Migration v11: calendar_events table recreated to extend the external_source CHECK constraint to include 'ics', and two new columns added — subscription_id (FK to ics_subscriptions with CASCADE delete) and user_modified (integer flag, default 0)
• Unique partial index idx_calendar_sub_extid on (subscription_id, external_calendar_id) prevents duplicate UIDs within a single ICS subscription while allowing the same UID across different subscriptions
• test:ics-sub test suite with 10 tests covering subscription CRUD, ICS event insertion, UNIQUE constraint enforcement, cascade delete, visibility filtering, and CHECK constraint validation