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/util/DateUtils.ets

@@ -0,0 +1,37 @@
+type DatePattern = 'yyyyMMdd' | 'yyyy-MM-dd' | 'yyyyMMddHHmmss' | 'HHmmss' | 'MM月dd日' | 'MM-dd HH:mm'
+
+export class DateUtils {
+
+  static formatDate(date: Date, pattern: DatePattern = 'yyyyMMdd'): string {
+    let year = ""
+    let month = ""
+    let day = ""
+    let hour = ""
+    let minute = ""
+    let second = ""
+    try {
+      year = date.getFullYear().toString();
+      month = ('0' + (date.getMonth() + 1)).slice(-2);
+      day = ('0' + date.getDate()).slice(-2);
+      hour = ('0' + date.getHours()).slice(-2);
+      minute = ('0' + date.getMinutes()).slice(-2);
+      second = ('0' + date.getSeconds()).slice(-2);
+    } catch (e) {
+      //日志获取失败
+      return ""
+    }
+    if (pattern == 'yyyy-MM-dd') {
+      return year + '-' + month + '-' + day
+    } else if (pattern == 'yyyyMMddHHmmss') {
+      return year + month + day + hour + minute + second
+    } else if (pattern == 'HHmmss') {
+      return hour + minute + second
+    } else if (pattern == 'MM月dd日') {
+      return month + '月' + day + '日'
+    } else if (pattern == 'MM-dd HH:mm') {
+      return month + '-' + day + ' ' + hour + ':' + minute
+    } else {
+      return year + month + day
+    }
+  }
+}