docs: add project documentation and update README

- Add `agent.md`: Complete maintenance reference covering project structure, API interactions, data flow, configuration, security, and operational procedures.
- Add `architecture.md`: High-level architecture overview including component map, data flow, design decisions, and security model.
- Update `README.md`: Add Apprise support documentation, manual deployment instructions, updated installation steps (bot admin requirement), and expanded payload mapping and troubleshooting sections.
- Improve `lib/Controller/WebhookController.php`: Enhance `saveBotPassword` validation to check for missing fields and validate the password content.
- Improve `lib/Service/TalkService.php`: Add `validateBotPassword` method for round-trip encryption testing and integrate it into `saveConfig`.
- Update `css/adminSettings.css`: Add styles for the new `.nc-app-frame` wrapper.
- Update `templates/adminSettings.php`: Refactor UI structure to use `.nc-app-frame` and improve layout of settings sections.

lib/Controller/WebhookController.php

@@ -319,9 +319,17 @@ class WebhookController extends Controller {
     public function saveBotPassword(): DataResponse {
         $body = file_get_contents('php://input');
         $data = @json_decode($body, true);
-        if (!is_array($data) || empty($data['bot_password'])) {
+        if (!is_array($data) || !isset($data['bot_password'])) {
             return new DataResponse(
-                ['error' => 'Invalid data'],
+                ['error' => 'Missing bot_password field'],
+                Http::STATUS_BAD_REQUEST,
+            );
+        }
+
+        $validation = $this->talkService->validateBotPassword($data['bot_password']);
+        if (!$validation['valid']) {
+            return new DataResponse(
+                ['error' => $validation['error']],
                 Http::STATUS_BAD_REQUEST,
             );
         }