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/include/config.php

@@ -2,8 +2,12 @@
 // Config file parser and writer.
 // Reads master.conf and the appropriate host*.conf based on running host.
 
-define('SCRIPTS_DIR', '/mnt/user/appdata/unraid_scripts');
+define('PLUGIN_CFG',  '/boot/config/plugins/varaverk/varaverk.cfg');
+
+$_vv_cfg = @parse_ini_file(PLUGIN_CFG) ?: [];
+define('SCRIPTS_DIR', $_vv_cfg['SCRIPTS_DIR'] ?? '/mnt/user/appdata/unraid_scripts');
 define('CONF_DIR',    SCRIPTS_DIR . '/Configurations');
+unset($_vv_cfg);
 
 function vv_get_hostname(): string {
     return trim(shell_exec('hostname -s') ?: '');