feat(vip): restructure membership settings into structured groups

Replace the pipe-delimited VIP configuration with structured groups and
accordions, matching the reference theme (Zibll) 1:1.

Settings:
- 会员等级 keeps only the nav buttons and the two level switches, plus the
  "must enable level 1 first" guard. Level identity fields (display name,
  intro, benefits HTML, icon) and 会员商品 move into the 一级会员/二级会员
  tabs of 会员购买选项, so each level is configured in one place.
- Level tab titles bind to the configured display name via a new
  titleKey/titleFallback hook in AksFormRenderer.
- 会员商品 is a repeater with exactly the reference fields: 执行价/原价/
  促销标签/标签颜色/会员有效时间/时长单位. The tag colour uses the full
  b+jb palette and now reaches the product card instead of a hardcoded
  jb-yellow.
- 会员续费 gains the 自定义商品 type backed by per-level renew-product
  groups; the discount becomes a 0.1-9.9 slider with float sanitizing.
- 会员升级 becomes the reference three-block accordion (month-to-month
  day-rate, jump to permanent, permanent to permanent), each with its own
  price, strikethrough price, promo tag and tag colour.
- 积分兑换明细 is a repeater (points/level/duration/unit) where the
  duration accepts the literal Permanent.

Runtime:
- PaymentRuntime normalizes the structured groups into purchasable rows
  (money normalization, palette validation, zero-price and out-of-range
  rows dropped) and no longer emits any *_raw strings.
- The catalog builder carries tag_class through and routes renewals to the
  renew-product group under 自定义商品.
- The points-exchange order note carries time/unit so month durations use
  calendar math instead of a 30-day approximation.

Dead code removed: parse_level_products, parse_packages,
parse_upgrade_product_line and their pipe-splitting, plus nine zero-call
PaymentRuntime proxy methods in HomeCms. No dual-format or migration path
was added; SchemaProvider already falls back to defaults when a stored
group value is not an array, so existing pipe strings degrade safely.

Verified: php -l on every changed PHP file, 655 Node contract tests passing
(14 new ones in vip-settings-structured-contract.test.cjs exercising the
real schema build and runtime normalization via a PHP harness), and the
admin SPA builds.

assets/js/pay-vip.js

@@ -124,7 +124,8 @@
       // Zibll 套餐卡：zib-widget vip-product relative text-center product-box
       // （右上 tag + 价格行 + 时长 badge，无标题行）。
       var product = node("div", "zib-widget vip-product relative text-center product-box");
-      if (item.discount_tag) append(product, node("div", "abs-right vip-tag badg jb-yellow", item.discount_tag));
+      // 标签颜色取后台「标签颜色」配置，未配置时回退参考主题默认的 jb-yellow。
+      if (item.discount_tag) append(product, node("div", "abs-right vip-tag badg " + (item.tag_class || "jb-yellow"), item.discount_tag));
       append(product, priceRow(mark, item.price_label || "", item.show_price_label || ""));
       if (item.days_label) append(product, node("div", "muted-2-color c-blue em09 p2-10 badg radius", item.days_label));
       append(label, product);