Add service API for Ladill Mail large attachment uploads.

Webmail can POST /api/v1/transfers with a mailbox address to create share links for files above 25 MB.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Http/Middleware/AuthenticateService.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Closure;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+/**
+ * Service-to-service auth for internal APIs. Validates the bearer token against
+ * per-consumer keys in config("{namespace}.service_api_keys").
+ */
+class AuthenticateService
+{
+    public function handle(Request $request, Closure $next, string $namespace = 'transfer'): Response
+    {
+        $token = (string) $request->bearerToken();
+        $caller = null;
+
+        if ($token !== '') {
+            foreach ((array) config("{$namespace}.service_api_keys", []) as $name => $key) {
+                if (is_string($key) && $key !== '' && hash_equals($key, $token)) {
+                    $caller = $name;
+                    break;
+                }
+            }
+        }
+
+        if ($caller === null) {
+            return response()->json(['error' => 'Unauthorized.'], 401);
+        }
+
+        $request->attributes->set('service_caller', $caller);
+
+        return $next($request);
+    }
+}