refactor: rename the theme brand and every identifier from AKSRT to Jio

Full-project rename. `git grep -i aksrt` is now empty apart from the
DBMigrator 3.3.0 changelog note that documents the rename itself.

Code identifiers
- PHP namespace AKSRT\ -> Jio\ (composer PSR-4 + 378 declarations)
- global constants AKSRT_* -> JIO_* (VERSION/DIR/URI, PAY_TYPE_*, CAPTCHA_*)
- procedural functions, hooks, options, meta keys, table names,
  cookies, query vars, ajax actions and nonces: aksrt_ -> jio_
- text domain aksrt -> jio; Theme Name -> Jio
- JS globals: aksrtData/aksrtAdminData/... -> jioData/jioAdminData/...,
  window.AKSRTCaptcha & friends -> window.JioCaptcha, Aksrt* -> Jio*
- Vue components Aks*.vue -> Jio*.vue (15 files renamed + imports)
- CSS classes/data-attrs/custom properties: aksrt- -> jio-
- REST namespace aksrt/v1 -> jio/v1 (incl. payment gateway callbacks)

Storage layer
- DB tables {prefix}aksrt_* -> {prefix}jio_*; SCHEMA_VERSION 3.2.0 -> 3.3.0
  so dbDelta creates the new names on install
- widget id_base aksrt_widget_* -> jio_widget_*
- uninstall.php drop list rebuilt from the actual migrator tables
  (dropped 3 stale entries, added the 17 missing ones)

Removed
- hardcoded https://api.aksrt.com/version.json default update endpoint;
  get_endpoint() now reads the 「更新端点」 setting and do_check() no-ops
  when it is empty

Files renamed: inc/helpers/aksrt-*.php -> jio-*.php (54),
assets/admin/src/components/form/Aks*.vue -> Jio*.vue (15).
Build artifacts regenerated: assets/css/build, assets/js/runtime,
assets/admin/build.

Verified: audit-psr4-paths errors=0, audit-admin-contracts errors=0
(warnings=56, unchanged baseline), 813/813 widget-system tests,
44/44 phpunit, php -l clean across all PHP.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/admin/submit-settings-reference-contract.test.cjs

@@ -11,7 +11,7 @@
  *    post_article_pay_vip_1_discount / post_article_pay_vip_2_discount /
  *    post_t_placeholder / post_c_placeholder；
  * 3) 专题（topics）相关字段不存在；
- * 4) 旧 AKSRT 私有字段（front_submit_*、post_article_title_strlen_limit_min/max、
+ * 4) 旧 Jio 私有字段（front_submit_*、post_article_title_strlen_limit_min/max、
  *    post_article_pay_price_min/max）已彻底移除，无双路兼容；
  * 5) 运行时（PostDisplay::get_submit_settings）只读取新键。
  */