Add label and title filtering to bd list (closes #45, bd-269)

- Add --label/-l flag to filter issues by labels (AND logic)
- Add --title flag to filter issues by title substring
- Add TitleSearch field to IssueFilter type
- Implement label and title filtering in SearchIssues
- Perfect for worktree-specific issue management

Examples:
  bd list --label worktree,feature-x
  bd list --title "authentication"
  bd list --label worktree --title "bug"

internal/storage/sqlite/sqlite.go

@@ -1151,6 +1151,12 @@ func (s *SQLiteStorage) SearchIssues(ctx context.Context, query string, filter t
 		args = append(args, pattern, pattern, pattern)
 	}
 
+	if filter.TitleSearch != "" {
+		whereClauses = append(whereClauses, "title LIKE ?")
+		pattern := "%" + filter.TitleSearch + "%"
+		args = append(args, pattern)
+	}
+
 	if filter.Status != nil {
 		whereClauses = append(whereClauses, "status = ?")
 		args = append(args, *filter.Status)
@@ -1171,6 +1177,14 @@ func (s *SQLiteStorage) SearchIssues(ctx context.Context, query string, filter t
 		args = append(args, *filter.Assignee)
 	}
 
+	// Label filtering: issue must have ALL specified labels
+	if len(filter.Labels) > 0 {
+		for _, label := range filter.Labels {
+			whereClauses = append(whereClauses, "id IN (SELECT issue_id FROM labels WHERE label = ?)")
+			args = append(args, label)
+		}
+	}
+
 	whereSQL := ""
 	if len(whereClauses) > 0 {
 		whereSQL = "WHERE " + strings.Join(whereClauses, " AND ")