feat(auth): OIDC/Keycloak SSO-Login (additiv) — v1.2.91

SSO per OpenID Connect (Authorization Code + PKCE) zusätzlich zum lokalen Login.
- Regeln: kein Auto-Provisioning (E-Mail muss als User existieren), Rolle aus DB (nie aus Token), lokaler Login+TOTP unangetastet.
- Migration 0040: oidc_settings (Singleton, client_secret_enc via secrets.Box) + users.oidc_subject.
- internal/services/oidc: Settings-Repo (write-only Secret) + lazy go-oidc Client (testbarer Authenticator-Seam).
- internal/handlers/oidc.go: GET/PUT /oidc/settings (admin), GET /auth/oidc/{settings,login,callback}. Flow-State (state/PKCE/nonce) stateless im 5-min signierten HttpOnly-Cookie (SameSite=Lax). email_verified erzwungen, opportunistisches sub-Linking, Session via setSessionCookie+Signer.
- session.SignBlob/VerifyBlob; users.Get/SetOIDCSubject; main.go-Wiring.
- Frontend: App.tsx /auth/me-Bootstrap (für Cookie-Session nach Callback), Login-SSO-Button + sso_error, Settings OIDC-Card, i18n de/en.
- Tests (guarded EG_FWTEST_DSN): Secret-Roundtrip + Callback (Rolle-aus-DB, no_account, disabled, unverified, nonce, state).
Deps: go-oidc/v3, x/oauth2. Scope v1: nur Login (kein SLO/Refresh).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/services/oidc/settings_test.go

@@ -0,0 +1,90 @@
+package oidc
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"git.netcell-it.de/projekte/edgeguard-native/internal/database"
+	"git.netcell-it.de/projekte/edgeguard-native/internal/services/secrets"
+)
+
+// migrateRetry umgeht die goose-Erst-Apply-Race, wenn mehrere guarded
+// Test-Pakete dieselbe frische DB parallel migrieren.
+func migrateRetry(ctx context.Context, dsn string) error {
+	var err error
+	for i := 0; i < 3; i++ {
+		if err = database.Migrate(ctx, dsn); err == nil {
+			return nil
+		}
+		time.Sleep(700 * time.Millisecond)
+	}
+	return err
+}
+
+// Guarded integration test: set EG_FWTEST_DSN (sonst skip).
+func testRepo(t *testing.T) *Repo {
+	t.Helper()
+	dsn := os.Getenv("EG_FWTEST_DSN")
+	if dsn == "" {
+		t.Skip("set EG_FWTEST_DSN to run the oidc settings test")
+	}
+	ctx := context.Background()
+	if err := migrateRetry(ctx, dsn); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	pool, err := database.Open(ctx, dsn)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	t.Cleanup(pool.Close)
+	box := secrets.New(t.TempDir() + "/master_key")
+	// Settings auf einen sauberen Default zurücksetzen.
+	if _, err := pool.Exec(ctx, `UPDATE oidc_settings SET enabled=false, issuer_url='', client_id='', client_secret_enc=NULL WHERE id=1`); err != nil {
+		t.Fatalf("reset: %v", err)
+	}
+	return New(pool, box)
+}
+
+func TestSettings_SecretWriteOnly(t *testing.T) {
+	r := testRepo(t)
+	ctx := context.Background()
+	str := func(s string) *string { return &s }
+
+	// 1) Neues Secret setzen.
+	if err := r.Update(ctx, UpdateInput{Enabled: true, IssuerURL: "https://idp.example/realms/x", ClientID: "eg", ClientSecret: str("s3cr3t")}); err != nil {
+		t.Fatal(err)
+	}
+	if has, _ := r.HasSecret(ctx); !has {
+		t.Fatal("HasSecret should be true after setting a secret")
+	}
+	got, err := r.ClientSecret(ctx)
+	if err != nil || got != "s3cr3t" {
+		t.Fatalf("ClientSecret = %q, %v; want s3cr3t", got, err)
+	}
+
+	// 2) Update mit nil → Secret bleibt unverändert.
+	if err := r.Update(ctx, UpdateInput{Enabled: true, IssuerURL: "https://idp.example/realms/x", ClientID: "eg2", ClientSecret: nil}); err != nil {
+		t.Fatal(err)
+	}
+	got, _ = r.ClientSecret(ctx)
+	if got != "s3cr3t" {
+		t.Fatalf("secret should be preserved on nil update, got %q", got)
+	}
+	if s, _ := r.Get(ctx); s.ClientID != "eg2" {
+		t.Fatalf("client_id should update to eg2, got %q", s.ClientID)
+	}
+
+	// 3) Update mit "" → Secret gelöscht.
+	if err := r.Update(ctx, UpdateInput{Enabled: false, IssuerURL: "", ClientID: "", ClientSecret: str("")}); err != nil {
+		t.Fatal(err)
+	}
+	if has, _ := r.HasSecret(ctx); has {
+		t.Fatal("HasSecret should be false after clearing the secret")
+	}
+	got, _ = r.ClientSecret(ctx)
+	if got != "" {
+		t.Fatalf("secret should be empty after clear, got %q", got)
+	}
+}