feat: add AI chat for repports

backend/internal/models/repository.go

@@ -666,3 +666,55 @@ func (r *Repository) DeleteReport(id, userID string) error {
 	_, err := r.db.Exec(`DELETE FROM reports WHERE id=$1 AND user_id=$2`, id, userID)
 	return err
 }
+
+func (r *Repository) GetReport(id, userID string) (*Report, error) {
+	rep := &Report{}
+	err := r.db.QueryRow(`
+		SELECT id, user_id, summary_id, context_excerpt, question, answer, status, error_msg, created_at
+		FROM reports WHERE id=$1 AND user_id=$2`, id, userID,
+	).Scan(&rep.ID, &rep.UserID, &rep.SummaryID, &rep.ContextExcerpt, &rep.Question, &rep.Answer, &rep.Status, &rep.ErrorMsg, &rep.CreatedAt)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	return rep, err
+}
+
+// ── Report messages ────────────────────────────────────────────────────────
+
+func (r *Repository) CreateReportMessage(reportID, role, content, status string) (*ReportMessage, error) {
+	msg := &ReportMessage{}
+	err := r.db.QueryRow(`
+		INSERT INTO report_messages (report_id, role, content, status)
+		VALUES ($1, $2, $3, $4)
+		RETURNING id, report_id, role, content, status, created_at`,
+		reportID, role, content, status,
+	).Scan(&msg.ID, &msg.ReportID, &msg.Role, &msg.Content, &msg.Status, &msg.CreatedAt)
+	return msg, err
+}
+
+func (r *Repository) UpdateReportMessage(id, status, content string) error {
+	_, err := r.db.Exec(`
+		UPDATE report_messages SET status=$1, content=$2 WHERE id=$3`,
+		status, content, id)
+	return err
+}
+
+func (r *Repository) ListReportMessages(reportID string) ([]ReportMessage, error) {
+	rows, err := r.db.Query(`
+		SELECT id, report_id, role, content, status, created_at
+		FROM report_messages WHERE report_id=$1
+		ORDER BY created_at ASC`, reportID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var msgs []ReportMessage
+	for rows.Next() {
+		var m ReportMessage
+		if err := rows.Scan(&m.ID, &m.ReportID, &m.Role, &m.Content, &m.Status, &m.CreatedAt); err != nil {
+			return nil, err
+		}
+		msgs = append(msgs, m)
+	}
+	return msgs, nil
+}