Fix plugin routing, missing includes, and make SCRIPTS_DIR configurable

- Rename varaverk.page → Varaverk.page: unRAID nginx only routes URLs
  starting with a capital letter (~^/[A-Z].*), lowercase caused 404
- Add require_once config.php to include/scheduler.php and include/docs.php:
  both used SCRIPTS_DIR constant without including the file that defines it
- Replace hardcoded SCRIPTS_DIR with cfg-file-backed setting: reads from
  /boot/config/plugins/varaverk/varaverk.cfg, falls back to default on first run
- Add Plugin Settings card to Config tab with scripts path field
- Add api/settings.php to write the cfg file (validates directory exists)

Plugin/usr/local/emhttp/plugins/varaverk/Varaverk.page

@@ -0,0 +1,40 @@
+Menu="Utilities:85"
+Title="Varaverk"
+Icon="varaverk.png"
+---
+<?php
+$plugin  = 'varaverk';
+$docroot = $docroot ?? $_SERVER['DOCUMENT_ROOT'] ?: '/usr/local/emhttp';
+$pluginDir = "$docroot/plugins/$plugin";
+
+// Determine active tab
+$tab = $_GET['tab'] ?? 'monitor';
+$validTabs = ['monitor', 'scheduler', 'config', 'docs'];
+if (!in_array($tab, $validTabs)) $tab = 'monitor';
+?>
+
+<link rel="stylesheet" href="/plugins/<?=$plugin?>/css/varaverk.css">
+
+<div id="varaverk-wrap">
+
+  <!-- Tab bar -->
+  <div id="vv-tabs">
+    <?php foreach ($validTabs as $t): ?>
+      <a href="?tab=<?=$t?>" class="vv-tab<?= $t === $tab ? ' active' : '' ?>">
+        <?= ucfirst($t) ?>
+      </a>
+    <?php endforeach; ?>
+  </div>
+
+  <!-- Tab content -->
+  <div id="vv-content">
+    <?php
+      $page = "$pluginDir/pages/$tab.php";
+      if (file_exists($page)) include $page;
+      else echo "<p>Page not found: $tab</p>";
+    ?>
+  </div>
+
+</div>
+
+<script src="/plugins/<?=$plugin?>/js/varaverk.js"></script>