fix(badges): keep the medal catalog from being cast to a string on save

user_medal_args was declared as type=json without sanitize_type, so
sanitize_field_value() fell through to sanitize_text_field((string) $value)
and stored the literal string "Array". validate() has no json shape check,
so the save reported success.

Consequence: parse_medal_catalog() json_decoded "Array" into an empty
catalog, the dictionary came back empty, and user_context() dropped every
owned badge — the front end showed "获取徽章" and the grant modal listed
nothing, hiding both the newly added and the pre-existing badges.

Add the missing sanitize_type to match its sibling level/integral fields,
and guard sanitize_field_value() so structured container types can never
reach the scalar fallback again. Mirrors the declaration in the Vue schema.

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

assets/admin/src/schema/sections/users/badge.js

@@ -134,6 +134,7 @@ export const badgeSchema = {
           key: 'user_medal_args',
           label: '分类与条目',
           type: 'json',
+          sanitizeType: 'array',
           default: defaultMedalArgs(),
           help: '由自定义页编辑：分类 → 条目（slug/名称/描述/图标/get_type/get_val）。仅手动授予用 manually_add。',
           dependsOn: { key: 'user_medal_s', value: true },