Add wallet balance widget to the profile menu (after Billing)

Wallet balance peek rendered as a menu row directly under Billing, backed by
a /wallet/balance endpoint (BillingClient) and guarded by Route::has. Also
opens Afia via a direct window event for reliability.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Http/Controllers/WalletBalanceController.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Services\Billing\BillingClient;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Cache;
+
+/**
+ * Lightweight wallet balance for the avatar dropdown widget.
+ */
+class WalletBalanceController extends Controller
+{
+    public function balance(Request $request, BillingClient $billing): JsonResponse
+    {
+        $publicId = (string) $request->user()->public_id;
+
+        $minor = Cache::remember("wallet_balance:{$publicId}", now()->addSeconds(30), function () use ($billing, $publicId) {
+            try {
+                return $billing->balanceMinor($publicId);
+            } catch (\Throwable) {
+                return null;
+            }
+        });
+
+        if ($minor === null) {
+            return response()->json(['available' => false]);
+        }
+
+        $currency = (string) config('billing.currency', 'GHS');
+
+        return response()->json([
+            'available' => true,
+            'balance_minor' => $minor,
+            'currency' => $currency,
+            'formatted' => $currency.' '.number_format($minor / 100, 2),
+        ]);
+    }
+}