feat: TypeScript + Electron v2 重构 - 纯桌面版

- 全面迁移到 TypeScript，严格类型定义
- 放弃 Web 版，专注 Electron 桌面应用
- 主进程模块化：main.ts, preload.ts, menu.ts, tray.ts, ipc.ts, utils.ts
- 渲染进程完整迁移所有功能组件
- 删除 PWA 相关文件 (sw.js, manifest.json)
- 删除 Web 版降级逻辑
- 保留所有核心功能：流式对话、多模型、Think推理、多模态、RAG知识库、Agent预设、历史管理
- 保留 Windows 11 Fluent Design 暗色主题样式

src/renderer/db/chat-db.ts

@@ -0,0 +1,154 @@
+/**
+ * ChatDB - IndexedDB 封装层
+ */
+
+import type { ChatSession } from '../types.js';
+
+export class ChatDB {
+  private dbName: string;
+  private version: number;
+  private db: IDBDatabase | null = null;
+
+  constructor(dbName = 'metona-ollama', version = 1) {
+    this.dbName = dbName;
+    this.version = version;
+  }
+
+  async init(): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const request = indexedDB.open(this.dbName, this.version);
+      request.onerror = () => {
+        console.error('[ChatDB] 数据库打开失败:', request.error);
+        reject(request.error);
+      };
+      request.onsuccess = () => {
+        this.db = request.result;
+        console.log('[ChatDB] 数据库已连接');
+        resolve();
+      };
+      request.onupgradeneeded = (event) => {
+        const db = (event.target as IDBOpenDBRequest).result;
+        if (!db.objectStoreNames.contains('sessions')) {
+          const sessionStore = db.createObjectStore('sessions', { keyPath: 'id' });
+          sessionStore.createIndex('updatedAt', 'updatedAt', { unique: false });
+          sessionStore.createIndex('model', 'model', { unique: false });
+        }
+        if (!db.objectStoreNames.contains('settings')) {
+          db.createObjectStore('settings', { keyPath: 'key' });
+        }
+      };
+    });
+  }
+
+  private _ensureDB(): void {
+    if (!this.db) throw new Error('数据库未初始化，请先调用 init()');
+  }
+
+  private _tx(storeName: string, mode: IDBTransactionMode = 'readonly'): IDBObjectStore {
+    this._ensureDB();
+    const tx = this.db!.transaction(storeName, mode);
+    return tx.objectStore(storeName);
+  }
+
+  async saveSession(session: ChatSession): Promise<string> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions', 'readwrite');
+      const request = store.put(session);
+      request.onsuccess = () => resolve(session.id);
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async getSession(id: string): Promise<ChatSession | null> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions');
+      const request = store.get(id);
+      request.onsuccess = () => resolve(request.result || null);
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async getAllSessions(): Promise<ChatSession[]> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions');
+      const request = store.getAll();
+      request.onsuccess = () => resolve(request.result || []);
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async deleteSession(id: string): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions', 'readwrite');
+      const request = store.delete(id);
+      request.onsuccess = () => resolve();
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async clearAll(): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions', 'readwrite');
+      const request = store.clear();
+      request.onsuccess = () => resolve();
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async importSessions(sessions: ChatSession[]): Promise<{ imported: number; skipped: number }> {
+    return new Promise((resolve, reject) => {
+      const tx = this.db!.transaction('sessions', 'readwrite');
+      const store = tx.objectStore('sessions');
+      let imported = 0;
+      let skipped = 0;
+
+      tx.oncomplete = () => resolve({ imported, skipped });
+      tx.onerror = () => reject(tx.error);
+
+      for (const session of sessions) {
+        if (!session.id || !Array.isArray(session.messages)) {
+          skipped++;
+          continue;
+        }
+        const getRequest = store.get(session.id);
+        getRequest.onsuccess = () => {
+          if (getRequest.result) {
+            skipped++;
+          } else {
+            store.put(session);
+            imported++;
+          }
+        };
+      }
+    });
+  }
+
+  async getSessionsByTimeRange(startTime: number, endTime: number): Promise<ChatSession[]> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('sessions');
+      const index = store.index('updatedAt');
+      const range = IDBKeyRange.bound(startTime, endTime);
+      const request = index.getAll(range);
+      request.onsuccess = () => resolve(request.result || []);
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async saveSetting(key: string, value: unknown): Promise<void> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('settings', 'readwrite');
+      const request = store.put({ key, value });
+      request.onsuccess = () => resolve();
+      request.onerror = () => reject(request.error);
+    });
+  }
+
+  async getSetting<T = unknown>(key: string, defaultValue: T | null = null): Promise<T> {
+    return new Promise((resolve, reject) => {
+      const store = this._tx('settings');
+      const request = store.get(key);
+      request.onsuccess = () => resolve(request.result ? request.result.value : defaultValue);
+      request.onerror = () => reject(request.error);
+    });
+  }
+}