refactor(settings): remove filing info config and readers

Drop the 备案信息 group (icp_filing, police_filing, footer_text) from the
global.common PHP/Vue schemas, the FacadeBulk readers and the
get_global_settings() payload. No frontend consumer existed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Admin/Schema/GlobalSchema.php

@@ -35,11 +35,6 @@ class GlobalSchema {
                             ]],
                             ['key' => 'thumbnail', 'label' => '懒加载预载图', 'type' => 'media', 'default' => get_template_directory_uri() . '/assets/img/thumbnail.svg'],
                         ]],
-                        ['key' => 'filing', 'title' => '备案信息', 'fields' => [
-                            ['key' => 'icp_filing', 'label' => 'ICP 备案号', 'type' => 'input', 'default' => ''],
-                            ['key' => 'police_filing', 'label' => '公安备案号', 'type' => 'input', 'default' => ''],
-                            ['key' => 'footer_text', 'label' => '页脚附加文字', 'type' => 'input', 'default' => ''],
-                        ]],
                     ],
                 ],
                 'logo' => [