feat: add vote_flashcard MCP tool

sqlite.go

@@ -43,6 +43,11 @@ func newSqliteStore(path string) (*sqliteStore, error) {
 		return nil, fmt.Errorf("sqlite ping: %w", err)
 	}
 
+	if _, err := db.Exec("PRAGMA foreign_keys = ON"); err != nil {
+		db.Close()
+		return nil, fmt.Errorf("enable foreign keys: %w", err)
+	}
+
 	goose.SetBaseFS(embedMigrations)
 
 	if err := goose.SetDialect("sqlite3"); err != nil {
@@ -233,6 +238,33 @@ func (s *sqliteStore) getByPublicIDAndVersion(ctx context.Context, publicID int6
 	return &e, nil
 }
 
+func (s *sqliteStore) saveVote(ctx context.Context, flashcardID int64, value int, user, repo, message string) (*vote, error) {
+	_, err := s.db.ExecContext(ctx,
+		`INSERT INTO vote (flashcard_id, value, "user", repo, message)
+		 VALUES (?, ?, ?, ?, ?)
+		 ON CONFLICT(flashcard_id, "user", repo)
+		 DO UPDATE SET value = excluded.value, message = excluded.message`,
+		flashcardID, value, user, repo, message,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("upsert vote: %w", err)
+	}
+
+	row := s.db.QueryRowContext(ctx,
+		`SELECT _id, flashcard_id, value, "user", repo, message, created
+		 FROM vote WHERE flashcard_id = ? AND "user" = ? AND repo = ?`,
+		flashcardID, user, repo,
+	)
+
+	var v vote
+	err = row.Scan(&v.ID, &v.FlashcardID, &v.Value, &v.User, &v.Repo, &v.Message, &v.Created)
+	if err != nil {
+		return nil, fmt.Errorf("read vote: %w", err)
+	}
+
+	return &v, nil
+}
+
 func (s *sqliteStore) tombstone(ctx context.Context, publicID int64, version int) (int64, error) {
 	result, err := s.db.ExecContext(ctx,
 		`INSERT INTO flashcard (public_id, version, note, delete_timestamp)