style: replace em dashes with hyphens throughout codebase

Replace all — with - in all source files (JS, CSS, HTML, JSON,
Markdown) for consistency and readability.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/styles/dashboard.css

@@ -1,6 +1,6 @@
 /**
  * Modul: Dashboard
- * Zweck: Styles für das Dashboard — Begrüßung, Widget-Grid, alle Widget-Typen, FAB-Speed-Dial
+ * Zweck: Styles für das Dashboard - Begrüßung, Widget-Grid, alle Widget-Typen, FAB-Speed-Dial
  * Abhängigkeiten: tokens.css, layout.css
  */
 
@@ -230,7 +230,7 @@
   margin-bottom: var(--space-1);
 }
 
-/* Widget hover lift (desktop) — dezent, max 1px */
+/* Widget hover lift (desktop) - dezent, max 1px */
 @media (min-width: 1024px) {
   .widget {
     transition: transform var(--transition-fast), box-shadow var(--transition-fast);