feat: fix push notifications and enhance PWA experience

- Fix InvalidCharacterError in push notifications with proper VAPID key validation
- Add attractive PWA install prompt component with cross-browser support
- Make notification settings always visible regardless of queue status
- Implement PWA install manager with user engagement detection
- Use SvelteKit navigation APIs instead of browser history API
- Add comprehensive error handling and logging
- Include cross-browser compatibility and responsive design
- Add development tooling improvements

Fixes push notification bugs and significantly improves PWA user experience
with modern, accessible interface components and proper error handling.

src/routes/components/NotificationSettings.svelte

@@ -64,6 +64,12 @@
 
 			<p class="text-sm text-gray-600 mb-4">
 				Get notified when your recipe extractions complete, even when InstaRecipe is not open.
+				{#if typeof window !== 'undefined'}
+					<!-- Check if we're on the homepage and queue appears empty -->
+					{#if window.location.pathname === '/' && !document.querySelector('[data-queue-item]')}
+						Start by adding some Instagram recipe URLs to see notifications in action!
+					{/if}
+				{/if}
 			</p>
 
 			<!-- Status -->