Initial commit: @b2c/first_page HarmonyOS stage-mode HAR

## Repository
- HarmonyOS stage-mode HAR module, consumed by host app
- No standalone build — hvigorw, oh_modules, and ../biz_quote absent here

## Architecture
### Feed Cards
- FirstPage.createNodeView dispatches cards by FirstPageConstant.KEY_*
- Card config from first_page_cards_config.json loaded by FirstPageCardsConfigLoader
- Public entrypoint: Index.ets

### Market Ranking (src/main/ets/market-ranking/)
- HTTP: MarketRankingDataFetcher fetches recommend_futures contracts
- HQ: MarketRankingHqRequestClient subscribes via 4106/frame 2201/scenario qht_qihuo_sort
- TCP reconnect rebuilds subscription from original HTTP contract list
- Async callbacks guarded by request/subscription versions

### Other Cards
- HotList, CommodityOptions, AiDiagnosis, AiRiseFall, SelfSelectedStock, CustomEntryList, FourEntryList
- Each has DataFetcher + HQ request client + NodeComponent

## Key Changes (from CardHarmonyOS reference)
- Added MetricId, PeriodId, SortOrder enums (MarketRankingModels.ets)
- Replaced string comparisons with enum switches in thirdColumnTitle/Value/Color
- Removed redundant undefined guards in thirdColumnColor/priceColor, delegated to riseFallColor
- Inlined priceColor(), use riseFallColor directly
- Tab bar Stack.height(30), Alignment.End (reverted from 46/TopEnd)
- Name column fontWeight removed (default regular)

src/main/ets/node/model/AiRiseFallNodeModel.ets

@@ -0,0 +1,50 @@
+/**
+ * AI 看涨跌接口响应
+ */
+export interface AiRiseFallResponse {
+  code: number
+  msg: string
+  data: AiRiseFallData
+}
+
+/**
+ * AI 看涨跌数据
+ */
+export interface AiRiseFallData {
+  date: string                           // 日期 "2026-06-01"
+  last_trade_date_accuracy: string       // 昨日正确率 "66.7"
+  last_twenty_trade_date_accuracy: string // 近20日正确率 "66.4"
+  rise: RiseFallListData                // 看涨列表
+  fall: RiseFallListData                // 看跌列表
+}
+
+/**
+ * 看涨/看跌列表数据
+ */
+export interface RiseFallListData {
+  count: number
+  data: RiseFallItem[]
+}
+
+/**
+ * 看涨/看跌项
+ */
+export interface RiseFallItem {
+  variety: string    // 品种代码 "SA"
+  name: string       // 合约名称 "纯碱2609"
+  contract: string   // 合约代码 "SA2609"
+  market: string     // 市场代码 "67"
+  forecast: number  // 预测方向 0=看涨, 1=看跌
+  accuracy: string   // 品种正确率 "80.0"
+  show_quote: number // 是否显示行情 1=显示
+}
+
+/**
+ * 合约行情数据（用于行情订阅）
+ */
+export interface ContractHqData {
+  contract: string
+  market: string
+  name: string
+  priceChg: number | null  // 涨跌幅，null 表示待开盘
+}