feat(ios): replace embedded website with initial native SwiftUI API client

Introduce real SwiftUI auth/dashboard/task/note/shopping screens, a bounded origin-bound URLSession transport and Keychain-backed native sessions. Archive the rejected WebKit renderer rather than embedding it for unfinished modules. Sixteen portable URL/contract/transport tests and Swift format/parsing pass on Linux; Apple SDK application and UI validation remains mandatory. This is an incomplete native slice, not full PWA parity or a release.

ios/Sources/ServerAddress.swift

@@ -1,6 +1,6 @@
 import Foundation
 
-struct ServerAddress: Equatable {
+struct ServerAddress: Equatable, Sendable {
     let url: URL
 
     init(_ input: String) throws {