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/lib/auth.svelte.ts

@@ -0,0 +1,94 @@
+import { goto } from '$app/navigation';
+
+const STORAGE_KEYS = {
+	token: 'wrenn_token',
+	userId: 'wrenn_user_id',
+	teamId: 'wrenn_team_id',
+	email: 'wrenn_email'
+} as const;
+
+function isTokenExpired(token: string): boolean {
+	try {
+		const payload = token.split('.')[1];
+		const decoded = atob(payload.replace(/-/g, '+').replace(/_/g, '/'));
+		const { exp } = JSON.parse(decoded);
+		return Date.now() / 1000 >= exp;
+	} catch {
+		return true;
+	}
+}
+
+function createAuth() {
+	let token = $state<string | null>(null);
+	let userId = $state<string | null>(null);
+	let teamId = $state<string | null>(null);
+	let email = $state<string | null>(null);
+	let initialized = $state(false);
+
+	// Initialize from localStorage synchronously at module load.
+	if (typeof window !== 'undefined') {
+		const stored = localStorage.getItem(STORAGE_KEYS.token);
+		if (stored && !isTokenExpired(stored)) {
+			token = stored;
+			userId = localStorage.getItem(STORAGE_KEYS.userId);
+			teamId = localStorage.getItem(STORAGE_KEYS.teamId);
+			email = localStorage.getItem(STORAGE_KEYS.email);
+		} else if (stored) {
+			// Expired — clean up.
+			for (const key of Object.values(STORAGE_KEYS)) {
+				localStorage.removeItem(key);
+			}
+		}
+		initialized = true;
+	}
+
+	const isAuthenticated = $derived(token !== null && !isTokenExpired(token));
+
+	return {
+		get token() {
+			return token;
+		},
+		get userId() {
+			return userId;
+		},
+		get teamId() {
+			return teamId;
+		},
+		get email() {
+			return email;
+		},
+		get isAuthenticated() {
+			return isAuthenticated;
+		},
+		get initialized() {
+			return initialized;
+		},
+
+		login(data: { token: string; user_id: string; team_id: string; email: string }) {
+			token = data.token;
+			userId = data.user_id;
+			teamId = data.team_id;
+			email = data.email;
+
+			localStorage.setItem(STORAGE_KEYS.token, data.token);
+			localStorage.setItem(STORAGE_KEYS.userId, data.user_id);
+			localStorage.setItem(STORAGE_KEYS.teamId, data.team_id);
+			localStorage.setItem(STORAGE_KEYS.email, data.email);
+		},
+
+		logout() {
+			token = null;
+			userId = null;
+			teamId = null;
+			email = null;
+
+			for (const key of Object.values(STORAGE_KEYS)) {
+				localStorage.removeItem(key);
+			}
+
+			goto('/login');
+		}
+	};
+}
+
+export const auth = createAuth();