feat: fetch subscription prices from server settings

- Add GET /api/v1/subscription/plans public endpoint (no auth needed)
  that reads prices from system_settings table
- Subscribe-plans page now loads prices from server on show
- Falls back to hardcoded defaults if API fails
- Add api.getPlans() to miniprogram API module

miniprogram/pages/subscribe-plans/subscribe-plans.js

@@ -4,10 +4,7 @@ var config = require('../../config/env')
 Page({
   data: {
     statusBarHeight: 44,
-    plans: [
-      { key: 'monthly', name: '月卡', price: 99, priceLabel: '¥99', desc: '约3.3元/天' },
-      { key: 'yearly', name: '年卡', price: 899, priceLabel: '¥899', desc: '省¥289', tag: '推荐' }
-    ],
+    plans: [],
     selected: 'yearly',
     purchasing: false,
     subscription: null,
@@ -28,9 +25,42 @@ Page({
   },
 
   onShow: function () {
+    this.loadPlans()
     this.loadSubscription()
   },
 
+  loadPlans: function () {
+    var self = this
+    api.getPlans().then(function (data) {
+      var plans = (data.plans || []).filter(function (p) { return p.key !== 'trial' }).map(function (p) {
+        var daily = p.days > 0 ? (p.price / p.days).toFixed(1) : 0
+        return {
+          key: p.key,
+          name: p.name,
+          price: p.price,
+          priceLabel: '¥' + p.price,
+          desc: p.key === 'yearly' ? '省¥' + ((p.price / 12 * 12) > 0 ? Math.round(self._monthlyPrice(data.plans) * 12 - p.price) : '') : '约' + daily + '元/天',
+          tag: p.key === 'yearly' ? '推荐' : ''
+        }
+      })
+      if (plans.length > 0) self.setData({ plans: plans })
+    }).catch(function () {
+      self.setData({
+        plans: [
+          { key: 'monthly', name: '月卡', price: 99, priceLabel: '¥99', desc: '约3.3元/天' },
+          { key: 'yearly', name: '年卡', price: 899, priceLabel: '¥899', desc: '省¥289', tag: '推荐' }
+        ]
+      })
+    })
+  },
+
+  _monthlyPrice: function (plans) {
+    for (var i = 0; i < plans.length; i++) {
+      if (plans[i].key === 'monthly') return plans[i].price
+    }
+    return 99
+  },
+
   loadSubscription: function () {
     var self = this
     api.getSubscription().then(function (sub) {

miniprogram/utils/api.js

@@ -17,6 +17,7 @@ module.exports = {
   unbindDevice: function (deviceId) { return http.post('/api/v1/device/unbind', deviceId ? { device_id: deviceId } : {}) },
 
   // Subscription
+  getPlans: function () { return http.get('/api/v1/subscription/plans') },
   getSubscription: function () { return http.get('/api/v1/subscription') },
   activateTrial: function () { return http.post('/api/v1/subscription/trial') },
   purchase: function (plan) { return http.post('/api/v1/subscription/purchase', { plan: plan }) },