feat(connection): 支持已保存登录凭证并重构首页仪表盘

新增登录凭证管理接口、数据表与前端选择器，连接创建、
编辑和测试现已支持复用已保存凭证

重构首页为管理驾驶舱，增加统计卡片、趋势与分布图、
活跃连接排行，并通过 summary 聚合数据统一驱动

packages/backend/src/index.ts

@@ -51,6 +51,7 @@ import quickCommandsRoutes from './quick-commands/quick-commands.routes';
 import terminalThemeRoutes from './terminal-themes/terminal-theme.routes';
 import appearanceRoutes from './appearance/appearance.routes';
 import sshKeysRouter from './ssh_keys/ssh_keys.routes'; 
+import loginCredentialsRouter from './login-credentials/login-credentials.routes';
 import quickCommandTagRoutes from './quick-command-tags/quick-command-tag.routes'; 
 import sshSuspendRouter from './ssh-suspend/ssh-suspend.routes';
 import { transfersRoutes } from './transfers/transfers.routes';
@@ -259,6 +260,7 @@ const startServer = () => {
     app.use('/api/v1/terminal-themes', terminalThemeRoutes);
     app.use('/api/v1/appearance', appearanceRoutes);
     app.use('/api/v1/ssh-keys', sshKeysRouter); 
+    app.use('/api/v1/login-credentials', loginCredentialsRouter);
     app.use('/api/v1/quick-command-tags', quickCommandTagRoutes);
     app.use('/api/v1/ssh-suspend', sshSuspendRouter); 
     app.use('/api/v1/transfers', transfersRoutes());