feat(pwa): installable app (Add to Home Screen) for Android + iOS

- manifest.json (standalone display, theme color, maskable icons 192/512).
- generated square icons + apple-touch-icon (180) from the logo.
- apple-mobile-web-app + theme-color meta in home.html.
- sw.js gets a no-op fetch handler so it meets installability criteria (still
  no caching). static.js serves .json/.webmanifest with correct MIME.
- Installing as a PWA also unlocks Web Push on iOS (Apple requires Add to Home Screen).
Build marker -> pwa1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/public/manifest.json

@@ -0,0 +1,16 @@
+{
+  "name": "BizGaze Connect",
+  "short_name": "Connect",
+  "description": "Chat, screen share, and video meetings for the BizGaze ecosystem.",
+  "start_url": "/home",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "portrait-primary",
+  "background_color": "#1F3B73",
+  "theme_color": "#1F3B73",
+  "icons": [
+    { "src": "/icon-192.png", "sizes": "192x192", "type": "image/png", "purpose": "any" },
+    { "src": "/icon-512.png", "sizes": "512x512", "type": "image/png", "purpose": "any" },
+    { "src": "/icon-512.png", "sizes": "512x512", "type": "image/png", "purpose": "maskable" }
+  ]
+}