Migrate app from Tauri to Electron

Replace the Tauri/sidecar architecture with an Electron main process. Adds an electron/ directory (main, preload, handlers, core integrations for @xmcl/*), electron-builder.yml, TypeScript electron config and declarations, and updated IPC utilities (ipc.ts) so frontend uses ipcRenderer/ipcMain. Removes Tauri sidecar and src-tauri artifacts, deletes sidecar sources and keys, updates .gitignore, VSCode recommendations, package scripts and icons, and updates documentation (README, AGENTS, DEV) and frontend stores/apis to reflect the Electron-based architecture and config/auth persistence changes.

electron/handlers/config.js

@@ -0,0 +1,29 @@
+"use strict";
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.registerConfigHandlers = registerConfigHandlers;
+const electron_1 = __importDefault(require("electron"));
+const { ipcMain } = electron_1.default;
+const config_1 = require("../config");
+function registerConfigHandlers() {
+    ipcMain.handle('config:get', () => {
+        try {
+            const config = (0, config_1.loadConfig)();
+            return { success: true, data: config, error: null };
+        }
+        catch (e) {
+            return { success: false, data: null, error: String(e) };
+        }
+    });
+    ipcMain.handle('config:save', (_event, config) => {
+        try {
+            (0, config_1.saveConfig)(config);
+            return { success: true, data: null, error: null };
+        }
+        catch (e) {
+            return { success: false, data: null, error: String(e) };
+        }
+    });
+}