Prepared SQL migrations for adding due_date support to todos.
Migrations:
- 003_add_due_date_to_todos.sql - Adds due_date column to todos table
- 004_add_due_date_to_global_todos.sql - Adds due_date column to global_todos table
Features:
- TIMESTAMPTZ column for timezone-aware dates
- Indexes on due_date for query performance
- Composite indexes on (completed, due_date) for filtering
Note: Backend and frontend implementation pending.
These migrations are ready to be applied when the feature is completed.
