Add bnfexpress signed admin client and AI Agent Filament UI

- Modules\Shared\Bnfexpress\BnfexpressAdminClient: HMAC-signed HTTP client
  for bnfexpress's admin API (EV FAQs, agent instructions, chat history),
  with a bnfexpress:smoke-test command and full unit coverage.
- New ai-agent module: Filament pages to manage EV FAQs, publish/roll back
  agent instruction versions, and browse EV chat history + transcripts.
- New manage_ai_agent permission (super_admin/admin).
- Recorded .ai/rules for the client's auth scheme and non-Resource
  Filament page/table testing gotchas.

app-modules/ai-agent/src/Providers/AiAgentServiceProvider.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Modules\AiAgent\Providers;
+
+use Illuminate\Support\ServiceProvider;
+
+class AiAgentServiceProvider extends ServiceProvider
+{
+    public function register(): void {}
+
+    public function boot(): void {}
+}