fix(db): add close_reason column to issues table (bd-uyu)

- Add migration 017_close_reason_column.go to create the column
- Update all INSERT statements to include close_reason
- Update all SELECT statements to include close_reason
- Update doctor.go to check for close_reason in schema validation
- Remove workaround code that batch-loaded close reasons from events table
- Fix migrations_test.go to include close_reason in test table schema

This fixes sync loops where close_reason values were silently dropped
because the DB lacked the column despite the struct having the field.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/storage/sqlite/labels.go

@@ -157,7 +157,7 @@ func (s *SQLiteStorage) GetIssuesByLabel(ctx context.Context, label string) ([]*
 	rows, err := s.db.QueryContext(ctx, `
 		SELECT i.id, i.content_hash, i.title, i.description, i.design, i.acceptance_criteria, i.notes,
 		       i.status, i.priority, i.issue_type, i.assignee, i.estimated_minutes,
-		       i.created_at, i.updated_at, i.closed_at, i.external_ref, i.source_repo
+		       i.created_at, i.updated_at, i.closed_at, i.external_ref, i.source_repo, i.close_reason
 		FROM issues i
 		JOIN labels l ON i.id = l.issue_id
 		WHERE l.label = ?