fix: Resolve SSR hydration mismatch and base path issues

- Replace onMount with  for isDemo state in contact page
  - Fixes SSR/client hydration mismatch causing content flicker
  - Ensures consistent rendering between server and client
  - Makes state reactive to URL parameter changes during navigation

- Use {base} path for banner CTA link instead of hardcoded '/contact'
  - Ensures compatibility with non-root deployment paths
  - Prevents broken links when deployed to subpaths like GitHub Pages
  - Maintains consistency with other site navigation

Improves user experience by eliminating layout shifts and ensures
robust deployment compatibility across different hosting environments.

Author: chris-stinemetz

src/routes/+layout.svelte

@@ -2,6 +2,7 @@
 	import '../app.scss';
 	import { Megaphone } from 'lucide-svelte';
 	import { page } from '$app/stores';
+	import { base } from '$app/paths';
 
 	let { children } = $props();
 
@@ -22,7 +23,7 @@
 					<Megaphone size={18} />
 				</span>
 				<span class="banner-message">Context Engine is launching soon!</span>
-				<a href="/contact?type=demo" class="banner-cta">Request Demo</a>
+				<a href="{base}/contact?type=demo" class="banner-cta">Request Demo</a>
 			</div>
 		</div>
 	</div>

src/routes/contact/+page.svelte

@@ -15,21 +15,17 @@
 	import { onMount } from 'svelte';
 
 	let formState: 'idle' | 'submitting' | 'success' | 'error' = $state('idle');
-	let isDemo = $state(false);
+
+	// Reactive to URL changes, works with SSR and client-side navigation
+	let isDemo = $derived($page.url.searchParams.get('type') === 'demo');
+
 	let formData = $state({
 		name: '',
 		email: '',
-		subject: '',
+		subject: isDemo ? 'Request Demo' : '',
 		message: ''
 	});
 
-	onMount(() => {
-		isDemo = $page.url.searchParams.get('type') === 'demo';
-		if (isDemo) {
-			formData.subject = 'Request Demo';
-		}
-	});
-
 	async function handleSubmit(event: SubmitEvent) {
 		event.preventDefault();
 		formState = 'submitting';