refactor: extract inline CSS/JS from views into separate asset files (20+ files)

Phase A — HTML removed from PHP files:
- RateLimitMiddleware.php: heredoc moved to views/errors/429.php
- public/index.php: inline HTML replaced with View::error()
- AuthMiddleware.php: <script> redirect replaced with <meta refresh>

Phase B — Inline CSS/JS extracted from views:
- CSS: landing.css (459 lines), legal.css (shared by terms+privacy)
- JS: 17 new files extracted from ~20 view files
  - main.js (layout sidebar + notifications)
  - dashboard-chart.js, server-show.js, server-services.js
  - nginx-manager.js, database-manager.js
  - terminal.js, team-show.js, team-index.js
  - server-list.js, server-permissions.js (shared by edit+create)
  - server-ssl.js, server-processes.js, system-users.js
  - admin-users.js, audit-log.js, admin-notifications.js, admin-security.js
  - notifications.js

Total: -3264 lines from views, +288 lines in new assets

public/index.php

@@ -23,12 +23,9 @@ try {
     $app->run();
 } catch (\Throwable $e) {
     http_response_code(500);
-    if (($_ENV['APP_DEBUG'] ?? false) === 'true') {
-        echo '<h1>Server Error</h1>';
-        echo '<pre>' . htmlspecialchars($e->getMessage()) . '</pre>';
-        echo '<pre>' . $e->getTraceAsString() . '</pre>';
-    } else {
-        echo '<h1>500 Internal Server Error</h1>';
-        echo '<p>An unexpected error occurred. Please check the logs.</p>';
+    if (isset($app)) {
+        $app->getView()->error(500);
     }
+    echo '<h1>500 Internal Server Error</h1>';
+    echo '<p>An unexpected error occurred.</p>';
 }