feat: implement PWA scaffold, dark design system, and 3-tab glassmorphism nav

- Add @serwist/next for PWA service worker (precaching, offline support)
- Create public/manifest.json with dark theme (#0a0a0f) and SVG icons
- Rewrite globals.css with full dark premium design system (Tailwind v4)
  - Design tokens: bg-deep, bg-card, gold, nur-purple, emerald, borders, text
  - Utility classes: .glass, .glass-light, .gold-gradient, .nur-gradient, .gold-purple-gradient
  - Prayer ring SVG styles
- Replace old 5-tab nav with 3-tab floating glassmorphism pill
  - Home (House), Nur center raised 56px gold-purple circle, Profile (User)
  - Active gold #D4AF37, inactive #666, safe-area-aware
- Create src/lib/api/wordpress.ts fetchAPI wrapper with JWT auth
- Update layout.tsx with manifest, apple-web-app, Viewport export

public/manifest.json

@@ -0,0 +1,23 @@
+{
+  "name": "Falah",
+  "short_name": "Falah",
+  "description": "Your Islamic lifestyle companion",
+  "start_url": "/home",
+  "display": "standalone",
+  "background_color": "#0a0a0f",
+  "theme_color": "#0a0a0f",
+  "icons": [
+    {
+      "src": "/icons/icon-192.svg",
+      "sizes": "192x192",
+      "type": "image/svg+xml",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "/icons/icon-512.svg",
+      "sizes": "512x512",
+      "type": "image/svg+xml",
+      "purpose": "any maskable"
+    }
+  ]
+}