feat(oidc): 支持自定义 OIDC 登录显示名称 (#6012)

* docs: add design spec for OIDC custom display name

Mirrors the existing Custom OAuth Provider name pattern so admins can
show a meaningful label instead of the hardcoded "OIDC" on the login
page and in related copy.

* feat(oidc): add configurable display name with OIDC fallback

* feat(oidc): use configured display name in provider name and status API

* feat(oidc): add display name field to default-theme OIDC settings

Claude-Session: https://claude.ai/code/session_01FDkWJqigJi9yE3HG5pjZP5

* feat(oidc): show configured display name on default-theme login button

* feat(oidc): add display name field to classic-theme OIDC settings

* feat(oidc): show configured display name on classic-theme login button

* fix(oidc): trim whitespace before applying display name fallback

* chore: remove internal design doc from PR

Design/planning docs are working artifacts for this session and
shouldn't be submitted to the upstream project.

* fix(oidc): lead with example in classic-theme display name placeholder

Reorders the combined placeholder to show the example first, then
the fallback note, matching the Custom OAuth Provider Name field's
placeholder convention (example-only) that this feature mirrors.

* fix(i18n): improve Russian grammar in OIDC display-name placeholder translation

Leads each clause with its condition/subject and adds the missing
verb, per PR review feedback.

* test(web): remove redundant OIDC harness tests

setting/system_setting/oidc.go

@@ -1,9 +1,14 @@
 package system_setting
 
-import "github.com/QuantumNous/new-api/setting/config"
+import (
+	"strings"
+
+	"github.com/QuantumNous/new-api/setting/config"
+)
 
 type OIDCSettings struct {
 	Enabled               bool   `json:"enabled"`
+	DisplayName           string `json:"display_name"`
 	ClientId              string `json:"client_id"`
 	ClientSecret          string `json:"client_secret"`
 	WellKnown             string `json:"well_known"`
@@ -23,3 +28,14 @@ func init() {
 func GetOIDCSettings() *OIDCSettings {
 	return &defaultOIDCSettings
 }
+
+// GetEffectiveDisplayName returns the admin-configured display name, or the
+// literal "OIDC" when none has been set. Centralizing this fallback keeps the
+// default in one place for both the OAuth provider name and the public
+// status payload.
+func (s *OIDCSettings) GetEffectiveDisplayName() string {
+	if trimmed := strings.TrimSpace(s.DisplayName); trimmed != "" {
+		return trimmed
+	}
+	return "OIDC"
+}

setting/system_setting/oidc_test.go

@@ -0,0 +1,47 @@
+package system_setting
+
+import (
+	"testing"
+
+	"github.com/QuantumNous/new-api/setting/config"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOIDCSettings_GetEffectiveDisplayName(t *testing.T) {
+	tests := []struct {
+		name        string
+		displayName string
+		want        string
+	}{
+		{name: "blank falls back to OIDC", displayName: "", want: "OIDC"},
+		{name: "custom name is returned verbatim", displayName: "Acme SSO", want: "Acme SSO"},
+		{name: "whitespace-only falls back to OIDC", displayName: "   ", want: "OIDC"},
+		{name: "surrounding whitespace is trimmed", displayName: "  Acme SSO  ", want: "Acme SSO"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			s := &OIDCSettings{DisplayName: tt.displayName}
+			assert.Equal(t, tt.want, s.GetEffectiveDisplayName())
+		})
+	}
+}
+
+func TestOIDCSettings_DisplayNamePersistenceRoundTrip(t *testing.T) {
+	settings := &OIDCSettings{DisplayName: "  Acme SSO  "}
+	manager := config.NewConfigManager()
+	manager.Register("oidc", settings)
+
+	saved := make(map[string]string)
+	require.NoError(t, manager.SaveToDB(func(key, value string) error {
+		saved[key] = value
+		return nil
+	}))
+	require.Equal(t, "  Acme SSO  ", saved["oidc.display_name"])
+
+	settings.DisplayName = ""
+	require.NoError(t, manager.LoadFromDB(saved))
+	assert.Equal(t, "  Acme SSO  ", settings.DisplayName)
+	assert.Equal(t, "Acme SSO", settings.GetEffectiveDisplayName())
+}