Fix SEC-09: hide admin nav links from non-admin users

- Add IsAdmin bool to PageData (embedded in all page view structs)
- Remove redundant IsAdmin from DashboardData
- Add isAdmin() helper to derive admin status from request claims
- Set IsAdmin in all page-level handlers that populate PageData
- Wrap admin-only nav links in base.html with {{if .IsAdmin}}
- Add tests: non-admin dashboard/profile hide admin links,
  admin dashboard shows them

Security: navigation links to /accounts, /audit, /policies,
and /pgcreds are now only rendered for admin users. Server-side
authorization (requireAdminRole middleware) was already in place;
this change removes the information leak of showing links that
return 403 to non-admin users.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/ui/ui_test.go

@@ -527,3 +527,121 @@ func TestAccountDetailShowsPGCredsSection(t *testing.T) {
 		t.Error("human account detail page must not include pgcreds-section")
 	}
 }
+
+// ---- SEC-09: admin nav link visibility tests ----
+
+// issueUserSession creates a human account with the "user" role (non-admin),
+// issues a JWT, tracks it, and returns the raw token string.
+func issueUserSession(t *testing.T, u *UIServer) string {
+	t.Helper()
+	acct, err := u.db.CreateAccount("regular-user", model.AccountTypeHuman, "")
+	if err != nil {
+		t.Fatalf("CreateAccount: %v", err)
+	}
+	if err := u.db.SetRoles(acct.ID, []string{"user"}, nil); err != nil {
+		t.Fatalf("SetRoles: %v", err)
+	}
+	tok, claims, err := token.IssueToken(u.privKey, testIssuer, acct.UUID, []string{"user"}, time.Hour)
+	if err != nil {
+		t.Fatalf("IssueToken: %v", err)
+	}
+	if err := u.db.TrackToken(claims.JTI, acct.ID, claims.IssuedAt, claims.ExpiresAt); err != nil {
+		t.Fatalf("TrackToken: %v", err)
+	}
+	return tok
+}
+
+// TestNonAdminDashboardHidesAdminNavLinks verifies that a non-admin user's
+// dashboard does not contain links to admin-only pages (SEC-09).
+func TestNonAdminDashboardHidesAdminNavLinks(t *testing.T) {
+	u := newTestUIServer(t)
+	mux := http.NewServeMux()
+	u.Register(mux)
+
+	userToken := issueUserSession(t, u)
+
+	req := authenticatedGET(t, userToken, "/dashboard")
+	rr := httptest.NewRecorder()
+	mux.ServeHTTP(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200; body: %s", rr.Code, rr.Body.String())
+	}
+
+	body := rr.Body.String()
+	for _, adminPath := range []string{
+		`href="/accounts"`,
+		`href="/audit"`,
+		`href="/policies"`,
+		`href="/pgcreds"`,
+	} {
+		if strings.Contains(body, adminPath) {
+			t.Errorf("non-admin dashboard contains admin link %s — SEC-09 violation", adminPath)
+		}
+	}
+
+	// Dashboard link should still be present.
+	if !strings.Contains(body, `href="/dashboard"`) {
+		t.Error("dashboard link missing from non-admin nav")
+	}
+}
+
+// TestAdminDashboardShowsAdminNavLinks verifies that an admin user's
+// dashboard contains all admin navigation links.
+func TestAdminDashboardShowsAdminNavLinks(t *testing.T) {
+	u := newTestUIServer(t)
+	mux := http.NewServeMux()
+	u.Register(mux)
+
+	adminToken, _, _ := issueAdminSession(t, u)
+
+	req := authenticatedGET(t, adminToken, "/dashboard")
+	rr := httptest.NewRecorder()
+	mux.ServeHTTP(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200; body: %s", rr.Code, rr.Body.String())
+	}
+
+	body := rr.Body.String()
+	for _, adminPath := range []string{
+		`href="/accounts"`,
+		`href="/audit"`,
+		`href="/policies"`,
+		`href="/pgcreds"`,
+	} {
+		if !strings.Contains(body, adminPath) {
+			t.Errorf("admin dashboard missing admin link %s", adminPath)
+		}
+	}
+}
+
+// TestNonAdminProfileHidesAdminNavLinks verifies that the profile page
+// also hides admin nav links for non-admin users (SEC-09).
+func TestNonAdminProfileHidesAdminNavLinks(t *testing.T) {
+	u := newTestUIServer(t)
+	mux := http.NewServeMux()
+	u.Register(mux)
+
+	userToken := issueUserSession(t, u)
+
+	req := authenticatedGET(t, userToken, "/profile")
+	rr := httptest.NewRecorder()
+	mux.ServeHTTP(rr, req)
+
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200; body: %s", rr.Code, rr.Body.String())
+	}
+
+	body := rr.Body.String()
+	for _, adminPath := range []string{
+		`href="/accounts"`,
+		`href="/audit"`,
+		`href="/policies"`,
+		`href="/pgcreds"`,
+	} {
+		if strings.Contains(body, adminPath) {
+			t.Errorf("non-admin profile page contains admin link %s — SEC-09 violation", adminPath)
+		}
+	}
+}