feat(theme): add Polarized and Suri purple dark themes

frontend/src/lib/__tests__/theme.test.ts

@@ -52,4 +52,16 @@ describe('custom themes', () => {
     expect(opt.previewAccent).toBe('#15803d');
     expect(opt.isRounded).toBe(true);
   });
+
+  it('supports polarized and suri built-in purple dark themes', () => {
+    setActiveTheme('polarized');
+    expect(getActiveTheme()).toBe('polarized');
+    expect(document.documentElement.getAttribute('data-theme')).toBe('polarized');
+    expect(document.documentElement.classList.contains('dark')).toBe(true);
+
+    setActiveTheme('suri');
+    expect(getActiveTheme()).toBe('suri');
+    expect(document.documentElement.getAttribute('data-theme')).toBe('suri');
+    expect(document.documentElement.classList.contains('dark')).toBe(true);
+  });
 });