Harden demo access and restore clean checks

src/lib/time-clock.ts

@@ -1,6 +1,11 @@
 /** Stored on entries clocked in before empty descriptions were allowed. */
 export const LEGACY_DEFAULT_CLOCK_DESCRIPTION = "Professional services";
 
+export function normalizeOptionalId(value?: string | null): string | null {
+  const trimmed = value?.trim();
+  return trimmed == null || trimmed === "" ? null : trimmed;
+}
+
 export function resolveEffectiveHourlyRate(
   enteredRate: number,
   client?: { defaultHourlyRate?: number | null } | null,