feat(gateway): enhance gateway process management with auto-reconnection

Improve Gateway lifecycle management with the following features:

- Add exponential backoff reconnection (1s-30s delay, max 10 attempts)
- Add health check monitoring every 30 seconds
- Add proper restart method with graceful shutdown
- Handle server-initiated notifications (channel status, chat messages)
- Add 'reconnecting' state for better UI feedback
- Enhance IPC handlers with isConnected and health check endpoints
- Update preload script with new event channels
- Improve type safety and error handling throughout

Also fixes several TypeScript errors and unused variable warnings.

src/components/layout/Sidebar.tsx

@@ -3,7 +3,7 @@
  * Navigation sidebar with menu items
  */
 import { useState, useEffect } from 'react';
-import { NavLink, useLocation } from 'react-router-dom';
+import { NavLink } from 'react-router-dom';
 import {
   Home,
   MessageSquare,
@@ -62,7 +62,6 @@ function NavItem({ to, icon, label, badge, collapsed }: NavItemProps) {
 }
 
 export function Sidebar() {
-  const location = useLocation();
   const sidebarCollapsed = useSettingsStore((state) => state.sidebarCollapsed);
   const setSidebarCollapsed = useSettingsStore((state) => state.setSidebarCollapsed);
   const devModeUnlocked = useSettingsStore((state) => state.devModeUnlocked);