Add honeycomb completion heatmap and data migration framework

- Add completion_summary endpoint data to residence detail response
- Track completed_from_column on task completions (overdue/due_soon/upcoming)
- Add GetCompletionSummary repo method with monthly aggregation
- Add one-time data migration framework (data_migrations table + registry)
- Add backfill migration to classify historical completions
- Add standalone backfill script for manual/dry-run usage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/database/database.go

@@ -188,6 +188,11 @@ func Migrate() error {
 		return fmt.Errorf("failed to run GoAdmin migrations: %w", err)
 	}
 
+	// Run one-time data migrations (backfills, etc.)
+	if err := RunDataMigrations(); err != nil {
+		return fmt.Errorf("failed to run data migrations: %w", err)
+	}
+
 	log.Info().Msg("Database migrations completed successfully")
 	return nil
 }