feat(ios): plugin natif Sign in with Google (CoachGoogleAuth)

- CoachGoogleAuth.swift : plugin Capacitor (SDK GoogleSignIn) → signIn() renvoie
  { idToken, email?, givenName? }, POSTé sur /auth/google/web (aud = client iOS).
  Garde #if canImport(GoogleSignIn) → le repo build même avant l'ajout du SDK.
- MainViewController : enregistre CoachGoogleAuthPlugin.
- AppDelegate : GIDSignIn.sharedInstance.handle(url) dans application(_:open:).
- project.pbxproj : CoachGoogleAuth.swift dans la target App.

⚠️ Xcode (Mac) : ajouter le SDK GoogleSignIn-iOS via SPM + GIDClientID/URL
scheme (reversed client id) dans Info.plist (cf. HANDOFF). Sans le SDK, le
bouton ne s'affiche pas (signIn rejette proprement).

ios/App/App.xcodeproj/project.pbxproj

@@ -38,6 +38,7 @@
 		E547F675B2F61C3475D2A787 /* LiveActivityManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = B93DA6B121E94B11DF938C90 /* LiveActivityManager.swift */; };
 		F1ABCDEF0123456789AB0001 /* CoachHealthRoute.swift in Sources */ = {isa = PBXBuildFile; fileRef = F1ABCDEF0123456789AB0002 /* CoachHealthRoute.swift */; };
 		A99E51A99E51A99E51A90001 /* CoachAppleAuth.swift in Sources */ = {isa = PBXBuildFile; fileRef = A99E51A99E51A99E51A90002 /* CoachAppleAuth.swift */; };
+		60061E60061E60061E060001 /* CoachGoogleAuth.swift in Sources */ = {isa = PBXBuildFile; fileRef = 60061E60061E60061E060002 /* CoachGoogleAuth.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -117,6 +118,7 @@
 		EBBF61A35F291A021BA75C60 /* CoachLiveActivityWidget.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = CoachLiveActivityWidget.swift; sourceTree = "<group>"; };
 		F1ABCDEF0123456789AB0002 /* CoachHealthRoute.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CoachHealthRoute.swift; sourceTree = "<group>"; };
 		A99E51A99E51A99E51A90002 /* CoachAppleAuth.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CoachAppleAuth.swift; sourceTree = "<group>"; };
+		60061E60061E60061E060002 /* CoachGoogleAuth.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CoachGoogleAuth.swift; sourceTree = "<group>"; };
 		F6BEAEF6F6274D61CAF22636 /* CoachWatchApp.swift */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = sourcecode.swift; path = CoachWatchApp.swift; sourceTree = "<group>"; };
 		FBFCA969A1B083CD3178D9B2 /* Info.plist */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 /* End PBXFileReference section */
@@ -202,6 +204,7 @@
 				D1BD5B1990CF3F2B9C5D0002 /* CoachWorkoutKit.swift */,
 				F1ABCDEF0123456789AB0002 /* CoachHealthRoute.swift */,
 				A99E51A99E51A99E51A90002 /* CoachAppleAuth.swift */,
+				60061E60061E60061E060002 /* CoachGoogleAuth.swift */,
 				E2CE6C2AA1DF4F3CAD6E0002 /* MainViewController.swift */,
 				504EC30B1FED79650016851F /* Main.storyboard */,
 				504EC30E1FED79650016851F /* Assets.xcassets */,
@@ -400,6 +403,7 @@
 				D1BD5B1990CF3F2B9C5D0001 /* CoachWorkoutKit.swift in Sources */,
 				F1ABCDEF0123456789AB0001 /* CoachHealthRoute.swift in Sources */,
 				A99E51A99E51A99E51A90001 /* CoachAppleAuth.swift in Sources */,
+				60061E60061E60061E060001 /* CoachGoogleAuth.swift in Sources */,
 				88F28EB12FBB330E00E8306E /* CoachWorkoutObserver.swift in Sources */,
 				E2CE6C2AA1DF4F3CAD6E0001 /* MainViewController.swift in Sources */,
 				21B242F8E61FB07C476C477C /* CoachLiveBridge.swift in Sources */,

ios/App/App/AppDelegate.swift

@@ -1,5 +1,8 @@
 import UIKit
 import Capacitor
+#if canImport(GoogleSignIn)
+import GoogleSignIn
+#endif
 
 @UIApplicationMain
 class AppDelegate: UIResponder, UIApplicationDelegate {
@@ -51,6 +54,12 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
     func applicationWillTerminate(_ application: UIApplication) {}
 
     func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey: Any] = [:]) -> Bool {
+        #if canImport(GoogleSignIn)
+        // Retour du flux OAuth Google (reversed client id URL scheme).
+        if GIDSignIn.sharedInstance.handle(url) {
+            return true
+        }
+        #endif
         return ApplicationDelegateProxy.shared.application(app, open: url, options: options)
     }
 

ios/App/App/CoachGoogleAuth.swift

@@ -0,0 +1,76 @@
+// CoachGoogleAuth.swift
+// Plugin Capacitor natif : Sign in with Google via le SDK GoogleSignIn-iOS.
+//
+// Usage côté JS (WebView) :
+//   const r = await window.Capacitor.Plugins.CoachGoogleAuth.signIn();
+//     → { idToken, email?, givenName?, familyName? }
+//     → reject("canceled") si annulé, sinon reject(message)
+//
+// L'`idToken` (JWT OIDC Google, aud = client iOS) est POSTé sur /auth/google/web
+// côté backend qui le vérifie contre le JWKS Google (GOOGLE_CLIENT_IDS doit
+// inclure le client iOS) puis pose le cookie de session.
+//
+// Prérequis Xcode (cf. HANDOFF) :
+// - SDK GoogleSignIn ajouté via SPM (https://github.com/google/GoogleSignIn-iOS)
+// - GIDClientID + URL scheme (reversed client id) dans Info.plist
+// - AppDelegate.application(_:open:) appelle GIDSignIn.sharedInstance.handle(url)
+//
+// Tant que le SDK n'est pas bundlé, le plugin compile (garde canImport) mais
+// signIn() rejette proprement.
+import Foundation
+import Capacitor
+#if canImport(GoogleSignIn)
+import GoogleSignIn
+#endif
+
+@objc(CoachGoogleAuthPlugin)
+public class CoachGoogleAuthPlugin: CAPPlugin, CAPBridgedPlugin {
+    public let identifier = "CoachGoogleAuthPlugin"
+    public let jsName = "CoachGoogleAuth"
+    public let pluginMethods: [CAPPluginMethod] = [
+        CAPPluginMethod(name: "isAvailable", returnType: CAPPluginReturnPromise),
+        CAPPluginMethod(name: "signIn", returnType: CAPPluginReturnPromise),
+    ]
+
+    @objc func isAvailable(_ call: CAPPluginCall) {
+        #if canImport(GoogleSignIn)
+        call.resolve(["available": true])
+        #else
+        call.resolve(["available": false, "reason": "GoogleSignIn SDK not bundled"])
+        #endif
+    }
+
+    @objc func signIn(_ call: CAPPluginCall) {
+        #if canImport(GoogleSignIn)
+        DispatchQueue.main.async {
+            guard let vc = self.bridge?.viewController else {
+                call.reject("No presenting view controller")
+                return
+            }
+            GIDSignIn.sharedInstance.signIn(withPresenting: vc) { result, error in
+                if let error = error {
+                    let nsErr = error as NSError
+                    if nsErr.code == GIDSignInError.canceled.rawValue {
+                        call.reject("canceled")
+                    } else {
+                        call.reject("Google sign-in failed: \(error.localizedDescription)")
+                    }
+                    return
+                }
+                guard let user = result?.user,
+                      let idToken = user.idToken?.tokenString else {
+                    call.reject("No id token returned by Google")
+                    return
+                }
+                var data: [String: Any] = ["idToken": idToken]
+                if let email = user.profile?.email { data["email"] = email }
+                if let given = user.profile?.givenName { data["givenName"] = given }
+                if let family = user.profile?.familyName { data["familyName"] = family }
+                call.resolve(data)
+            }
+        }
+        #else
+        call.reject("GoogleSignIn SDK not bundled in this build")
+        #endif
+    }
+}

ios/App/App/MainViewController.swift

@@ -25,6 +25,9 @@ class MainViewController: CAPBridgeViewController {
         // Plugin natif Sign in with Apple — signIn() natif (AuthenticationServices)
         // → identity_token POSTé sur /auth/apple/web (cf. CoachAppleAuth.swift).
         bridge?.registerPluginInstance(CoachAppleAuthPlugin())
+        // Plugin natif Sign in with Google — signIn() via SDK GoogleSignIn
+        // → id_token POSTé sur /auth/google/web (cf. CoachGoogleAuth.swift).
+        bridge?.registerPluginInstance(CoachGoogleAuthPlugin())
     }
 
     override func viewDidLoad() {