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>

scripts/generate-icons.js

@@ -53,7 +53,7 @@ function createAppleTouchSvg() {
   return createLogoSvg(180);
 }
 
-/** Favicon (32x32): simplified — just gradient background with house */
+/** Favicon (32x32): simplified - just gradient background with house */
 function createFaviconSvg() {
   return createLogoSvg(32);
 }