feat(frontend): add apiFetch wrapper for automatic auth token injection

Centralizes auth token management into a reusable apiFetch() helper and getAuthHeaders() utility, eliminating inline Bearer token logic across all frontend files.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

frontend/src/lib/components/today/CurrentAppointment.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { authStore } from '$lib/stores/auth.svelte';
+	import { apiFetch } from '$lib/utils/api';
 	import { ensureBusinessInfo, getBusinessInfo } from '$lib/stores/businessInfo.svelte';
 	import { SvelteDate } from 'svelte/reactivity';
 	import { toast } from 'svelte-sonner';
@@ -179,12 +179,8 @@
 	async function fetchCurrentAndNext() {
 		loading = true;
 		try {
-			const response = await fetch('/api/admin/today/current-next', {
-				method: 'GET',
-				headers: {
-					'Content-Type': 'application/json',
-					Authorization: `Bearer ${authStore.currentToken}`
-				}
+			const response = await apiFetch('/api/admin/today/current-next', {
+				headers: { 'Content-Type': 'application/json' }
 			});
 
 			if (response.ok) {