refactor: Cleanup git state - commit all staged changes

Major refactoring cleanup:
- Add new controller architecture (class-controller-*.php)
- Add new settings-v2 UI (views/settings-v2/)
- Add new CSS architecture (agentic-sidebar.css, tokens)
- Add esbuild build pipeline (scripts/build.js, package.json)
- Add composer dependencies (vendor/)
- Add frontend src directory (assets/js/src/index.jsx)
- Add documentation files
- Remove old/obsolete files (class-settings.php, old CSS)

This commits all pending changes from previous refactoring efforts.

vendor/jawira/plantuml/resources/download.php

@@ -0,0 +1,24 @@
+<?php
+// Call API
+$options = [
+  'http' => [
+    'method' => 'GET',
+    'header' => "Accept: application/vnd.github+json\r\n" . "X-GitHub-Api-Version: 2022-11-28\r\n" . "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36\r\n"
+  ]
+];
+$context = stream_context_create($options);
+$url = 'https://api.github.com/repos/plantuml/plantuml/releases/latest';
+echo 'Calling Github API', PHP_EOL;
+$data = file_get_contents($url, false, $context);
+
+// Get download url
+$pattern = <<<'REGEXP'
+#"browser_download_url": "(https://github\.com/plantuml/plantuml/releases/download/v\d+\.\d+\.\d+/plantuml\.jar)"#m
+REGEXP;
+preg_match($pattern, $data, $matches);
+
+// Download
+echo 'Downloading ', $matches[1] ?? '<null>', PHP_EOL;
+$stream = fopen($matches[1] ?? '<null>', 'r', false, $context);
+file_put_contents(__DIR__ . '/../bin/plantuml.jar', $stream);
+echo 'Done!', PHP_EOL;

vendor/jawira/plantuml/resources/version.txt

@@ -0,0 +1 @@
+v1.2026.6