Fix PWA install: static manifest.json + proper SVG icon

- Replace blob: manifest (ignored by Chrome) with static manifest.json
- Replace data: URL icon with real icon.svg file
- Link manifest and apple-touch-icon directly in <head>
- Remove blob/data URL generation from app.js

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

nginx.conf

@@ -29,6 +29,12 @@ server {
         add_header Cache-Control "no-cache, no-store, must-revalidate";
     }
 
+    # Manifest – short cache so icon/name updates roll out quickly
+    location = /manifest.json {
+        add_header Cache-Control "no-cache, no-store, must-revalidate";
+        add_header Access-Control-Allow-Origin "*";
+    }
+
     # SPA fallback
     location / {
         try_files $uri $uri/ /index.html;