Fix TypeScript compilation: remove deprecated baseUrl, add missing imports, fix type narrowing

- Remove deprecated baseUrl from tsconfig.app.json (TS 6.0 error)
- Add missing AlertCircle and Button imports in Dashboard.tsx
- Cast Sidebar onNavigate arg to fix View type mismatch

tsc exits 0, vite build exits 0

src/App.tsx

@@ -151,7 +151,7 @@ function AppContent() {
       <Sidebar
         onAddConnection={() => setConnectionDialogOpen(true)}
         activeView={view.type}
-        onNavigate={handleNavigate}
+        onNavigate={(v) => handleNavigate(v as View)}
       />
       <main className="flex-1 overflow-hidden">
         {renderMainContent()}