feat: add models cache store and fix search placeholder truncation

- Add useModelsStore with 30s cache for model list to reduce API calls
  - Refactor SystemPage to use cached models from store
  - Shorten ConfigPage search placeholder to prevent text truncation

src/stores/index.ts

@@ -7,3 +7,4 @@ export { useThemeStore } from './useThemeStore';
 export { useLanguageStore } from './useLanguageStore';
 export { useAuthStore } from './useAuthStore';
 export { useConfigStore } from './useConfigStore';
+export { useModelsStore } from './useModelsStore';

src/stores/useModelsStore.ts

@@ -0,0 +1,76 @@
+/**
+ * 模型列表状态管理（带缓存）
+ */
+
+import { create } from 'zustand';
+import { modelsApi } from '@/services/api/models';
+import { CACHE_EXPIRY_MS } from '@/utils/constants';
+import type { ModelInfo } from '@/utils/models';
+
+interface ModelsCache {
+  data: ModelInfo[];
+  timestamp: number;
+  apiBase: string;
+}
+
+interface ModelsState {
+  models: ModelInfo[];
+  loading: boolean;
+  error: string | null;
+  cache: ModelsCache | null;
+
+  fetchModels: (apiBase: string, apiKey?: string, forceRefresh?: boolean) => Promise<ModelInfo[]>;
+  clearCache: () => void;
+  isCacheValid: (apiBase: string) => boolean;
+}
+
+export const useModelsStore = create<ModelsState>((set, get) => ({
+  models: [],
+  loading: false,
+  error: null,
+  cache: null,
+
+  fetchModels: async (apiBase, apiKey, forceRefresh = false) => {
+    const { cache, isCacheValid } = get();
+
+    // 检查缓存
+    if (!forceRefresh && isCacheValid(apiBase) && cache) {
+      set({ models: cache.data, error: null });
+      return cache.data;
+    }
+
+    set({ loading: true, error: null });
+
+    try {
+      const list = await modelsApi.fetchModels(apiBase, apiKey);
+      const now = Date.now();
+
+      set({
+        models: list,
+        loading: false,
+        cache: { data: list, timestamp: now, apiBase }
+      });
+
+      return list;
+    } catch (error: any) {
+      const message = error?.message || 'Failed to fetch models';
+      set({
+        error: message,
+        loading: false,
+        models: []
+      });
+      throw error;
+    }
+  },
+
+  clearCache: () => {
+    set({ cache: null, models: [] });
+  },
+
+  isCacheValid: (apiBase) => {
+    const { cache } = get();
+    if (!cache) return false;
+    if (cache.apiBase !== apiBase) return false;
+    return Date.now() - cache.timestamp < CACHE_EXPIRY_MS;
+  }
+}));