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/resources/views/filament/pages/manage-agent-instructions.blade.php

@@ -0,0 +1,13 @@
+<x-filament-panels::page>
+    <x-filament::section heading="Active Instruction">
+        @if ($active)
+            <pre class="whitespace-pre-wrap text-sm">{{ $active['content'] ?? '' }}</pre>
+        @elseif ($activeError)
+            <p class="text-sm text-danger-600">Could not load the active instruction: {{ $activeError }}</p>
+        @else
+            <p class="text-sm text-gray-500">No active instruction.</p>
+        @endif
+    </x-filament::section>
+
+    {{ $this->table }}
+</x-filament-panels::page>