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()
+        }
+    }
+}

Lendair/Package.swift

@@ -11,6 +11,10 @@ let package = Package(
         .library(
             name: "Lendair",
             targets: ["Lendair"]
+        ),
+        .executable(
+            name: "LendairApp",
+            targets: ["LendairApp"]
         )
     ],
     targets: [
@@ -22,8 +26,16 @@ let package = Package(
                 "Services",
                 "ViewModels",
                 "Views"
+            ],
+            linkerSettings: [
+                .linkedFramework("UIKit", .when(platforms: [.iOS]))
             ]
         ),
+        .executableTarget(
+            name: "LendairApp",
+            dependencies: ["Lendair"],
+            path: "App"
+        ),
         .testTarget(
             name: "LendairTests",
             dependencies: ["Lendair"],