fix(robustness): parseInt radix, minGapDays null-guard, log silent catches (#14)

- parseInt(month/year) now passes radix 10 consistently.
- minGap eligibility guards null/undefined (c.minGapDays != null && > 0).
- The corrupt-localStorage load and the createEmployee catch now console.warn
  instead of swallowing the error silently.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/app.js

@@ -26,8 +26,9 @@ try {
       state.settings = { moderatorsPerDay: parsed.settings.moderatorsPerDay };
     }
   }
-} catch {
-  // Corrupt storage — start fresh
+} catch (e) {
+  // Corrupt storage — start fresh, but leave a breadcrumb for debugging
+  console.warn('Gespeicherter Zustand konnte nicht gelesen werden, starte leer:', e);
 }
 
 // Persist immediately. Used by the debounced saveState and the flush handlers.