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/components/oikos-install-prompt.js

@@ -27,7 +27,7 @@ class OikosInstallPrompt extends HTMLElement {
   }
 
   connectedCallback() {
-    // Bereits im Standalone-Modus — nichts anzeigen
+    // Bereits im Standalone-Modus - nichts anzeigen
     if (
       window.matchMedia('(display-mode: standalone)').matches ||
       navigator.standalone === true