[client] Pass stored email as login hint from UI and keep it on logout

Follow the CLI pattern: the Wails UI now reads the account email from the
user-owned profile state file and passes it as the OIDC login_hint on login
and session extend, since the daemon-side fallback runs as root and cannot
see the user's state file. Logout no longer deletes the stored email, so a
later login preselects the account at the IdP; profile removal remains the
operation that deletes it.

client/ui/authsession/service.go

@@ -9,6 +9,7 @@ import (
 	"google.golang.org/grpc/codes"
 	gstatus "google.golang.org/grpc/status"
 
+	"github.com/netbirdio/netbird/client/internal/profilemanager"
 	"github.com/netbirdio/netbird/client/proto"
 )
 
@@ -60,9 +61,17 @@ func (s *Session) RequestExtend(ctx context.Context, p ExtendStartParams) (Exten
 
 	// a request from the UI implies a graphical session, which the daemon cannot detect itself
 	req := &proto.RequestExtendAuthSessionRequest{HasGraphicalSession: true}
-	if p.Hint != "" {
-		h := p.Hint
-		req.Hint = &h
+	hint := p.Hint
+	if hint == "" {
+		pm := profilemanager.NewProfileManager()
+		if active, perr := pm.GetActiveProfile(); perr == nil {
+			if state, serr := pm.GetProfileState(active.ID); serr == nil {
+				hint = state.Email
+			}
+		}
+	}
+	if hint != "" {
+		req.Hint = &hint
 	}
 
 	resp, err := cli.RequestExtendAuthSession(ctx, req)