feat(forgot-password): add AuthHeader for consistent auth page branding

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

frontend/src/routes/forgot-password/+page.svelte

@@ -1,10 +1,12 @@
 <script lang="ts">
 import { m } from '$lib/paraglide/messages.js';
+import AuthHeader from '../AuthHeader.svelte';
 
 let { form }: { form?: { error?: string; success?: boolean } } = $props();
 </script>
 
-<div class="relative flex min-h-screen flex-col bg-surface">
+<div class="flex min-h-screen flex-col bg-canvas">
+	<AuthHeader />
 	<div class="flex flex-1 items-center justify-center px-4">
 		<div class="w-full max-w-sm">
 			<!-- Logo -->