Fix 404 errors: Move favicon files to static directory and update all references

static/favicon.svg

@@ -0,0 +1,6 @@
+<svg width="32" height="32" viewBox="0 0 32 32" fill="none" xmlns="http://www.w3.org/2000/svg">
+  <rect x="4" y="4" width="24" height="24" rx="5" fill="#2563eb"/>
+  <rect x="4" y="4" width="24" height="6" rx="2" fill="#1e40af"/>
+  <rect x="9" y="14" width="14" height="10" rx="3" fill="#fff"/>
+  <text x="16" y="22" text-anchor="middle" font-size="10" font-family="Segoe UI, Arial, sans-serif" fill="#2563eb" font-weight="bold" dominant-baseline="middle">15</text>
+</svg> 

static/manifest.json

@@ -7,8 +7,8 @@
   "theme_color": "#2563eb",
   "description": "Open Source Web-App für Kalender- und Datumsberechnungen.",
   "icons": [
-    { "src": "/favicon.png", "sizes": "32x32", "type": "image/png" },
-    { "src": "/favicon.ico", "sizes": "48x48 64x64 128x128 256x256", "type": "image/x-icon" },
+    { "src": "/static/favicon.png", "sizes": "32x32", "type": "image/png" },
+    { "src": "/static/favicon.ico", "sizes": "48x48 64x64 128x128 256x256", "type": "image/x-icon" },
     { "src": "/static/logo.svg", "sizes": "any", "type": "image/svg+xml" }
   ]
 } 

static/service-worker.js

@@ -2,9 +2,9 @@ const CACHE_NAME = 'datumsrechner-cache-v1';
 const urlsToCache = [
   '/',
   '/static/style.css',
-  '/favicon.ico',
-  '/favicon.png',
-  '/logo.svg',
+  '/static/favicon.ico',
+  '/static/favicon.png',
+  '/static/logo.svg',
 ];
 self.addEventListener('install', event => {
   event.waitUntil(