feat: 性能优化 + Bug修复 + 搜索增强

- expo-image 替换 RN Image（VideoCard/LiveCard/BigVideoCard/CommentItem，recyclingKey）
- DanmakuList Animated.Value 对象池，减少 GC 压力
- FlatList 性能参数：windowSize=7 / maxToRenderPerBatch=6 / removeClippedSubviews
- bilibili.ts 请求去重（getVideoDetail/getPlayUrl）
- SESSDATA 迁移至 expo-secure-store（utils/secureStorage.ts，启动自动迁移）
- 主题系统扩展：新增 sheetBg/modalBg/modalText/placeholder/iconDefault/danger 等 token
- 多组件深色模式适配：DownloadSheet/LivePlayer/NativeVideoPlayer/DownloadProgressBtn/CommentItem/LoginModal
- 搜索页增强：搜索建议 + 热搜榜（hooks/useSearch.ts + app/search.tsx）
- LoginModal 修复轮询竞态（cancelled flag + try-catch）
- 修复 downloads.tsx 冗余三元表达式

hooks/useSearch.ts

@@ -1,6 +1,25 @@
-import { useState, useCallback, useRef } from 'react';
-import { searchVideos } from '../services/bilibili';
-import type { VideoItem } from '../services/types';
+import { useState, useCallback, useRef, useEffect } from 'react';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import { searchVideos, getSearchSuggest, getHotSearch } from '../services/bilibili';
+import type { VideoItem, SearchSuggestItem, HotSearchItem } from '../services/types';
+
+const HISTORY_KEY = 'search_history';
+const MAX_HISTORY = 20;
+
+export type SearchSort = 'default' | 'pubdate' | 'view';
+
+async function loadHistory(): Promise<string[]> {
+  try {
+    const raw = await AsyncStorage.getItem(HISTORY_KEY);
+    return raw ? JSON.parse(raw) : [];
+  } catch {
+    return [];
+  }
+}
+
+async function saveHistory(history: string[]) {
+  await AsyncStorage.setItem(HISTORY_KEY, JSON.stringify(history));
+}
 
 export function useSearch() {
   const [keyword, setKeyword] = useState('');
@@ -8,18 +27,74 @@ export function useSearch() {
   const [page, setPage] = useState(1);
   const [loading, setLoading] = useState(false);
   const [hasMore, setHasMore] = useState(true);
+  const [sort, setSort] = useState<SearchSort>('default');
+  const [history, setHistory] = useState<string[]>([]);
+  const [suggestions, setSuggestions] = useState<SearchSuggestItem[]>([]);
+  const [hotSearches, setHotSearches] = useState<HotSearchItem[]>([]);
   const loadingRef = useRef(false);
+  const suggestTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const currentSort = useRef<SearchSort>('default');
 
-  const search = useCallback(async (kw: string, reset = false) => {
+  // Load history & hot searches on mount
+  useEffect(() => {
+    loadHistory().then(setHistory);
+    getHotSearch().then(setHotSearches);
+  }, []);
+
+  // Debounced suggestions
+  useEffect(() => {
+    if (suggestTimer.current) clearTimeout(suggestTimer.current);
+    if (!keyword.trim() || keyword.trim().length < 1) {
+      setSuggestions([]);
+      return;
+    }
+    suggestTimer.current = setTimeout(async () => {
+      const items = await getSearchSuggest(keyword.trim());
+      setSuggestions(items);
+    }, 300);
+    return () => {
+      if (suggestTimer.current) clearTimeout(suggestTimer.current);
+    };
+  }, [keyword]);
+
+  const addToHistory = useCallback(async (kw: string) => {
+    const trimmed = kw.trim();
+    if (!trimmed) return;
+    setHistory(prev => {
+      const filtered = prev.filter(h => h !== trimmed);
+      const next = [trimmed, ...filtered].slice(0, MAX_HISTORY);
+      saveHistory(next);
+      return next;
+    });
+  }, []);
+
+  const removeFromHistory = useCallback(async (kw: string) => {
+    setHistory(prev => {
+      const next = prev.filter(h => h !== kw);
+      saveHistory(next);
+      return next;
+    });
+  }, []);
+
+  const clearHistory = useCallback(async () => {
+    setHistory([]);
+    await AsyncStorage.removeItem(HISTORY_KEY);
+  }, []);
+
+  const search = useCallback(async (kw: string, reset = false, sortOverride?: SearchSort) => {
     if (!kw.trim() || loadingRef.current) return;
     loadingRef.current = true;
     setLoading(true);
+    setSuggestions([]);
+    const activeSort = sortOverride ?? currentSort.current;
     const currentPage = reset ? 1 : page;
+    const orderParam = activeSort === 'pubdate' ? 'pubdate' : activeSort === 'view' ? 'click' : '';
     try {
-      const items = await searchVideos(kw, currentPage);
+      const items = await searchVideos(kw, currentPage, orderParam);
       if (reset) {
         setResults(items);
         setPage(2);
+        addToHistory(kw);
       } else {
         setResults(prev => [...prev, ...items]);
         setPage(p => p + 1);
@@ -31,12 +106,28 @@ export function useSearch() {
       loadingRef.current = false;
       setLoading(false);
     }
-  }, [page]);
+  }, [page, addToHistory]);
+
+  const changeSort = useCallback((newSort: SearchSort) => {
+    setSort(newSort);
+    currentSort.current = newSort;
+    if (keyword.trim()) {
+      search(keyword, true, newSort);
+    }
+  }, [keyword, search]);
 
   const loadMore = useCallback(() => {
     if (!keyword.trim() || loadingRef.current || !hasMore) return;
     search(keyword, false);
   }, [keyword, hasMore, search]);
 
-  return { keyword, setKeyword, results, loading, hasMore, search, loadMore };
+  return {
+    keyword, setKeyword,
+    results, loading, hasMore,
+    search, loadMore,
+    sort, changeSort,
+    history, removeFromHistory, clearHistory,
+    suggestions,
+    hotSearches,
+  };
 }