Added basic frontend (#1)

Reviewed-on: wrenn/sandbox#1
Co-authored-by: pptx704 <rafeed@omukk.dev>
Co-committed-by: pptx704 <rafeed@omukk.dev>

frontend/src/routes/auth/github/callback/+page.svelte

@@ -0,0 +1,28 @@
+<script lang="ts">
+	import { goto } from '$app/navigation';
+	import { page } from '$app/stores';
+	import { auth } from '$lib/auth.svelte';
+
+	const params = $page.url.searchParams;
+	const error = params.get('error');
+
+	if (error) {
+		goto(`/login?error=${encodeURIComponent(error)}`);
+	} else {
+		const token = params.get('token');
+		const userId = params.get('user_id');
+		const teamId = params.get('team_id');
+		const email = params.get('email');
+
+		if (token && userId && teamId && email) {
+			auth.login({ token, user_id: userId, team_id: teamId, email });
+			goto('/dashboard');
+		} else {
+			goto('/login?error=missing_token');
+		}
+	}
+</script>
+
+<div class="flex min-h-screen items-center justify-center">
+	<p class="text-[13px] text-[var(--color-text-secondary)]">Signing you in...</p>
+</div>