[client] Verify the SSO login came back for the hinted account

login_hint is a suggestion the IdP may ignore: with a silent flow configured
(DisablePromptLogin or max_age=0) and a live IdP session for another account,
the login completes with that account's token. On a registered peer the
management server rejects it as a user mismatch, but on a fresh profile the
peer silently registers under the wrong account and the profile is then bound
to it — every later login follows the stored hint straight back.

After the token exchange, compare the ID token's email against the hint the
flow was sent with. On a mismatch, do not log in to management with the token;
run one more round asking the IdP to re-decide the account (prompt=login, via
ForceAccountPrompt — DisablePromptLogin still wins there). If the prompted
round also comes back different, proceed with a warning: the address may
legitimately have changed, and refusing forever would lock the user out of the
profile while the management server still rejects a token that does not own
the peer. A token or profile with no email to compare is not judged.

The retry differs per platform because of who opens the browser:

- CLI (netbird login foreground) and Android run the whole flow in one
  process, so the mismatch retries automatically: the browser reopens with
  the account prompt within the same login attempt.
- On desktop the login is split between the daemon and the GUI: Login hands
  the authorize URL to the GUI, WaitSSOLogin blocks for the token, and only
  the GUI can open a browser. A new URL cannot be handed out from inside
  WaitSSOLogin (its response has no field for one, kept that way to avoid a
  proto change), so the daemon arms forceAccountPrompt, fails the round with
  "connect again to choose the account", and builds the next Login's flow
  with the prompt — the user's next connect is the retry.

The flag and the flow annotations live in daemon memory only; SwitchProfile
drops them so the previous profile's hint cannot judge the next profile's
token. The device code flow has no prompt parameter (RFC 8628), so a prompted
round there runs as-is and a repeated mismatch is let through with the
warning rather than looping.

client/server/login_account_test.go

@@ -0,0 +1,125 @@
+package server
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/client/internal"
+	"github.com/netbirdio/netbird/client/internal/auth"
+	"github.com/netbirdio/netbird/client/proto"
+)
+
+type stubOAuthFlow struct {
+	token auth.TokenInfo
+}
+
+func (f *stubOAuthFlow) RequestAuthInfo(context.Context) (auth.AuthFlowInfo, error) {
+	return auth.AuthFlowInfo{}, nil
+}
+
+func (f *stubOAuthFlow) WaitToken(context.Context, auth.AuthFlowInfo) (auth.TokenInfo, error) {
+	return f.token, nil
+}
+
+func (f *stubOAuthFlow) GetClientID(context.Context) string {
+	return "stub-client"
+}
+
+func TestWaitSSOLogin_WrongAccountArmsPromptAndFails(t *testing.T) {
+	s := newSSOTestServer(t, "user@example.com", false, "other@example.com")
+	attempts := 0
+	s.loginAttemptFn = func(context.Context, string, string) (internal.StatusType, error) {
+		attempts++
+		return "", nil
+	}
+
+	resp, err := s.WaitSSOLogin(context.Background(), &proto.WaitSSOLoginRequest{UserCode: "code"})
+	require.Error(t, err)
+	require.Nil(t, resp)
+	require.Equal(t, 0, attempts, "the wrong account's token reached the management login")
+	require.True(t, s.forceAccountPrompt, "the next login was not armed to ask for the account")
+	require.Nil(t, s.oauthAuthFlow.flow, "the mismatched flow stayed cached for reuse")
+
+	status, stateErr := internal.CtxGetState(s.rootCtx).Status()
+	require.NoError(t, stateErr)
+	require.Equal(t, internal.StatusNeedsLogin, status, "the mismatch must stay retryable")
+}
+
+func TestWaitSSOLogin_WrongAccountAfterPromptProceeds(t *testing.T) {
+	s := newSSOTestServer(t, "user@example.com", true, "other@example.com")
+	attempts := 0
+	s.loginAttemptFn = func(context.Context, string, string) (internal.StatusType, error) {
+		attempts++
+		return "", nil
+	}
+
+	resp, err := s.WaitSSOLogin(context.Background(), &proto.WaitSSOLoginRequest{UserCode: "code"})
+	require.NoError(t, err, "a prompted round must not error again on a mismatch")
+	require.NotNil(t, resp)
+	require.Equal(t, "other@example.com", resp.Email)
+	require.Equal(t, 1, attempts)
+	require.False(t, s.forceAccountPrompt)
+}
+
+func TestWaitSSOLogin_MatchingAccountProceeds(t *testing.T) {
+	s := newSSOTestServer(t, "user@example.com", false, "User@Example.com")
+	attempts := 0
+	s.loginAttemptFn = func(context.Context, string, string) (internal.StatusType, error) {
+		attempts++
+		return "", nil
+	}
+
+	resp, err := s.WaitSSOLogin(context.Background(), &proto.WaitSSOLoginRequest{UserCode: "code"})
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	require.Equal(t, 1, attempts)
+	require.False(t, s.forceAccountPrompt)
+}
+
+func TestWaitSSOLogin_NoHintIsNotJudged(t *testing.T) {
+	s := newSSOTestServer(t, "", false, "whoever@example.com")
+	attempts := 0
+	s.loginAttemptFn = func(context.Context, string, string) (internal.StatusType, error) {
+		attempts++
+		return "", nil
+	}
+
+	_, err := s.WaitSSOLogin(context.Background(), &proto.WaitSSOLoginRequest{UserCode: "code"})
+	require.NoError(t, err)
+	require.Equal(t, 1, attempts)
+	require.False(t, s.forceAccountPrompt)
+}
+
+func TestSwitchProfile_DropsAccountPromptAndPendingFlow(t *testing.T) {
+	s, ctx, _, _, _ := setupServerWithProfile(t)
+	s.forceAccountPrompt = true
+	cancelled := false
+	s.oauthAuthFlow = oauthAuthFlow{
+		flow:       &stubOAuthFlow{},
+		hint:       "user@example.com",
+		waitCancel: func() { cancelled = true },
+	}
+
+	_, err := s.SwitchProfile(ctx, nil)
+	require.NoError(t, err)
+	require.False(t, s.forceAccountPrompt, "the prompt flag leaked across a profile switch")
+	require.Nil(t, s.oauthAuthFlow.flow, "the previous profile's flow leaked across a profile switch")
+	require.Empty(t, s.oauthAuthFlow.hint)
+	require.True(t, cancelled, "the pending wait was not cancelled")
+}
+
+func newSSOTestServer(t *testing.T, hint string, accountPrompted bool, tokenEmail string) *Server {
+	t.Helper()
+	s := New(internal.CtxInitState(context.Background()), "console", "", false, false, false, false)
+	s.oauthAuthFlow = oauthAuthFlow{
+		flow:            &stubOAuthFlow{token: auth.TokenInfo{Email: tokenEmail}},
+		info:            auth.AuthFlowInfo{UserCode: "code"},
+		expiresAt:       time.Now().Add(time.Minute),
+		hint:            hint,
+		accountPrompted: accountPrompted,
+	}
+	return s
+}