Fix CI/CD pipeline issues from code review FRE-4690

P1: Fix TestFlight deployment — add LendairApp executable target,
    use xcodebuild archive/export instead of swift build for IPA
P2: Fix swift-format — use built-in 'swift format lint' (Swift 5.6+)
    instead of external 'swift-format' binary
P3: Create missing index.html for Vite build entry point
P3: Update vercel-action from v30 to v25 (better maintained)

Lendair/App/main.swift

@@ -0,0 +1,11 @@
+import SwiftUI
+import Lendair
+
+@main
+struct LendairApp: SwiftUI.App {
+    var body: some Scene {
+        WindowGroup {
+            MainTabView()
+        }
+    }
+}