Complete re-validation remediation: KMP architecture, iOS platform, XCUITest rewrite

Phases 1-6 of fixes.md — closes all 13 issues from codex_issues_2.md re-validation:

KMP Architecture:
- Fix subscription purchase/restore response contract (VerificationResponse aligned)
- Add feature benefits auth token + APILayer init flow
- Remove ResidenceFormScreen direct API bypass (use APILayer)
- Wire paywall purchase/restore to real SubscriptionApi calls

iOS Platform:
- Add iOS Keychain token storage via Swift KeychainHelper
- Implement Google Sign-In via ASWebAuthenticationSession (GoogleSignInManager)
- DocumentViewModelWrapper observes DataManager for auto-updates
- Add missing accessibility identifiers (document, task columns, Google Sign-In)

XCUITest Rewrite:
- Rewrite test infrastructure: zero sleep() calls, accessibility ID lookups
- Create AuthCriticalPathTests and NavigationCriticalPathTests
- Delete 14 legacy brittle test files (Suite0-10, templates)
- Fix CaseraTests module import (@testable import Casera)

All platforms build clean. TEST BUILD SUCCEEDED.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

iosApp/CaseraUITests/CriticalPath/AuthCriticalPathTests.swift

@@ -0,0 +1,111 @@
+import XCTest
+
+/// Critical path tests for authentication flows.
+///
+/// Validates login, logout, registration entry, and password reset entry.
+/// Zero sleep() calls — all waits are condition-based.
+final class AuthCriticalPathTests: XCTestCase {
+    var app: XCUIApplication!
+
+    override func setUp() {
+        super.setUp()
+        continueAfterFailure = false
+        app = TestLaunchConfig.launchApp()
+    }
+
+    override func tearDown() {
+        app = nil
+        super.tearDown()
+    }
+
+    // MARK: - Login
+
+    func testLoginWithValidCredentials() {
+        let login = LoginScreen(app: app)
+        guard login.emailField.waitForExistence(timeout: 15) else {
+            // Already logged in — verify main screen
+            let main = MainTabScreen(app: app)
+            XCTAssertTrue(main.isDisplayed, "Main screen should be visible when already logged in")
+            return
+        }
+
+        let user = TestFixtures.TestUser.existing
+        login.login(email: user.email, password: user.password)
+
+        let main = MainTabScreen(app: app)
+        XCTAssertTrue(
+            main.residencesTab.waitForExistence(timeout: 15),
+            "Should navigate to main screen after successful login"
+        )
+    }
+
+    func testLoginWithInvalidCredentials() {
+        let login = LoginScreen(app: app)
+        guard login.emailField.waitForExistence(timeout: 15) else {
+            return // Already logged in, skip
+        }
+
+        login.login(email: "invaliduser", password: "wrongpassword")
+
+        // Should stay on login screen — email field should still exist
+        XCTAssertTrue(
+            login.emailField.waitForExistence(timeout: 10),
+            "Should remain on login screen after invalid credentials"
+        )
+
+        // Tab bar should NOT appear
+        let tabBar = app.tabBars.firstMatch
+        XCTAssertFalse(tabBar.exists, "Tab bar should not appear after failed login")
+    }
+
+    // MARK: - Logout
+
+    func testLogoutFlow() {
+        let login = LoginScreen(app: app)
+        if login.emailField.waitForExistence(timeout: 15) {
+            let user = TestFixtures.TestUser.existing
+            login.login(email: user.email, password: user.password)
+        }
+
+        let main = MainTabScreen(app: app)
+        guard main.residencesTab.waitForExistence(timeout: 15) else {
+            XCTFail("Main screen did not appear")
+            return
+        }
+
+        main.logout()
+
+        // Should be back on login screen
+        let loginAfterLogout = LoginScreen(app: app)
+        XCTAssertTrue(
+            loginAfterLogout.emailField.waitForExistence(timeout: 15),
+            "Should return to login screen after logout"
+        )
+    }
+
+    // MARK: - Registration Entry
+
+    func testSignUpButtonNavigatesToRegistration() {
+        let login = LoginScreen(app: app)
+        guard login.emailField.waitForExistence(timeout: 15) else {
+            return // Already logged in, skip
+        }
+
+        let register = login.tapSignUp()
+        XCTAssertTrue(register.isDisplayed, "Registration screen should appear after tapping Sign Up")
+    }
+
+    // MARK: - Forgot Password Entry
+
+    func testForgotPasswordButtonExists() {
+        let login = LoginScreen(app: app)
+        guard login.emailField.waitForExistence(timeout: 15) else {
+            return // Already logged in, skip
+        }
+
+        XCTAssertTrue(
+            login.forgotPasswordButton.waitForExistence(timeout: 5),
+            "Forgot password button should exist on login screen"
+        )
+    }
+}