Fix stale admin specs and expand Jest coverage

- Fix SettingsView/SegmentsView specs to match current dialog-based
  confirm flows instead of stale assumptions.
- Fix FeatureDetail delete confirmation: deleteConfirmName was
  referenced but never declared, so the type-to-confirm gate was dead
  code with no input or disabled binding.
- Extract the router's auth guard as authGuard so it can be tested
  directly instead of duplicated inline in specs; add missing
  allowAuthenticated and redirect-query coverage.
- Add specs for previously untested modules: api/client.ts (401
  refresh/retry/queueing), LoginView, RegisterView, AcceptInviteView,
  stores/theme.ts, utils/validation.ts, ConditionEditor, and
  RuleGroupEditor.

src/admin/tests/unit/utils/validation.spec.ts

@@ -0,0 +1,52 @@
+import { describe, it, expect } from '@jest/globals';
+import { validateEmail } from '@/utils/validation';
+
+describe('validateEmail', () => {
+  describe('WhenTheValueIsEmpty', () => {
+    it('ThenItReturnsAnEmailRequiredMessage', () => {
+      expect(validateEmail('')).toBe('Email required');
+    });
+  });
+
+  describe('WhenTheValueIsOnlyWhitespace', () => {
+    it('ThenItReturnsAnEmailRequiredMessage', () => {
+      expect(validateEmail('   ')).toBe('Email required');
+    });
+  });
+
+  describe('WhenTheValueIsAValidEmail', () => {
+    it('ThenItReturnsTrue', () => {
+      expect(validateEmail('jane@example.com')).toBe(true);
+    });
+  });
+
+  describe('WhenTheValueHasSurroundingWhitespace', () => {
+    it('ThenItIsTrimmedBeforeValidationAndReturnsTrue', () => {
+      expect(validateEmail('  jane@example.com  ')).toBe(true);
+    });
+  });
+
+  describe('WhenTheValueIsMissingTheAtSymbol', () => {
+    it('ThenItReturnsAnInvalidEmailMessage', () => {
+      expect(validateEmail('jane.example.com')).toBe('Invalid email');
+    });
+  });
+
+  describe('WhenTheValueIsMissingTheDomain', () => {
+    it('ThenItReturnsAnInvalidEmailMessage', () => {
+      expect(validateEmail('jane@example')).toBe('Invalid email');
+    });
+  });
+
+  describe('WhenTheValueContainsSpaces', () => {
+    it('ThenItReturnsAnInvalidEmailMessage', () => {
+      expect(validateEmail('jane doe@example.com')).toBe('Invalid email');
+    });
+  });
+
+  describe('WhenTheValueHasMultipleAtSymbols', () => {
+    it('ThenItReturnsAnInvalidEmailMessage', () => {
+      expect(validateEmail('jane@doe@example.com')).toBe('Invalid email');
+    });
+  });
+});