feat: refactor member to pay-per-use gravity purchase; mv webview to clipboard+browser

- member.vue: rewrite from subscription plans (free/growth/sprint) to
  H5-only pay-per-use gravity purchase with quantity selector + QR code
- user.vue: gravity card replacing quota card, add share/contribute/H5-buy
  entry points, plus gravity acquisition modal (share/contribute/buy)
- share.vue: layout fix (flex column), smarter copyLink with cached URL,
  WeChat timeline hint instead of open-type
- share.controller.ts: add GET /:shareCode redirect route (IP record + 302)
- interview.vue: guest mode fix, H5 buy modal, clipboard copy instead of
  webview for mini-program
- App.vue: handleH5UrlParams for ?token=&buy=gravity auto-login
- composables/useGravityPurchase.ts: reusable gravity purchase composable
- remove webview.vue (no longer used), replace with clipboard+browser flow
- AGENTS.md: sync all above changes, fix duplicate numbering

zhiyin-app/src/App.vue

@@ -6,8 +6,28 @@ onLaunch(() => {
   // #ifdef MP-WEIXIN
   initPrivacy()
   // #endif
+  // #ifdef H5
+  handleH5UrlParams()
+  // #endif
 })
 
+// #ifdef H5
+function handleH5UrlParams() {
+  const params = new URLSearchParams(window.location.search)
+  const token = params.get('token')
+  const buy = params.get('buy')
+  if (token) {
+    uni.setStorageSync('token', token)
+  }
+  if (buy === 'gravity') {
+    // 延迟等 app 初始化完成再跳转
+    setTimeout(() => {
+      uni.navigateTo({ url: '/pages/member/member' })
+    }, 300)
+  }
+}
+// #endif
+
 // #ifdef MP-WEIXIN
 function initPrivacy() {
   if (wx.onNeedPrivacyAuthorization) {