add reading settings sync

internal/repository/user_repo.go

@@ -152,6 +152,41 @@ func (r *UserRepo) UpdatePassword(ctx context.Context, id, newHash string) error
 	return nil
 }
 
+// GetReadingPrefs returns the raw JSONB bytes for the user's reading
+// prefs (empty object when never set). The frontend owns the shape, so
+// we round-trip the payload verbatim — no server-side schema enforced.
+func (r *UserRepo) GetReadingPrefs(ctx context.Context, id string) ([]byte, error) {
+	const q = `SELECT reading_prefs FROM users WHERE id = $1 LIMIT 1`
+	var raw []byte
+	err := r.pg.Pool.QueryRow(ctx, q, id).Scan(&raw)
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, ErrUserNotFound
+		}
+		return nil, fmt.Errorf("get reading prefs: %w", err)
+	}
+	if len(raw) == 0 {
+		raw = []byte("{}")
+	}
+	return raw, nil
+}
+
+// UpdateReadingPrefs overwrites the user's reading prefs blob. Caller is
+// responsible for validating that `prefsJSON` is well-formed JSON (the
+// handler does this by re-marshalling the decoded struct before calling
+// in).
+func (r *UserRepo) UpdateReadingPrefs(ctx context.Context, id string, prefsJSON []byte) error {
+	const q = `UPDATE users SET reading_prefs = $2::jsonb, updated_at = now() WHERE id = $1`
+	tag, err := r.pg.Pool.Exec(ctx, q, id, prefsJSON)
+	if err != nil {
+		return fmt.Errorf("update reading prefs: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return ErrUserNotFound
+	}
+	return nil
+}
+
 // MarkEmailVerified sets email_verified_at = now() if not already set.
 func (r *UserRepo) MarkEmailVerified(ctx context.Context, id string) error {
 	const q = `UPDATE users SET email_verified_at = now(), updated_at = now()