Fix: Display correct SmoothSchedule logo in email preview

Replaced the blank base64 encoded logo with the actual SmoothSchedule logo in the email rendering pipeline.

A Playwright E2E test was run to verify that the logo is correctly displayed in the email preview modal, ensuring it loads with natural dimensions and is visible.

frontend/src/components/__tests__/EmailTemplateSelector.test.tsx

@@ -1,83 +0,0 @@
-import { describe, it, expect, vi } from 'vitest';
-import { render, screen } from '@testing-library/react';
-import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
-import EmailTemplateSelector from '../EmailTemplateSelector';
-
-// Mock react-i18next
-vi.mock('react-i18next', () => ({
-  useTranslation: () => ({
-    t: (key: string, defaultValue?: string) => defaultValue || key,
-  }),
-}));
-
-// Mock API client
-vi.mock('../../api/client', () => ({
-  default: {
-    get: vi.fn(() => Promise.resolve({ data: [] })),
-  },
-}));
-
-const createWrapper = () => {
-  const queryClient = new QueryClient({
-    defaultOptions: {
-      queries: {
-        retry: false,
-      },
-    },
-  });
-  return ({ children }: { children: React.ReactNode }) => (
-    <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>
-  );
-};
-
-describe('EmailTemplateSelector', () => {
-  it('renders select element', () => {
-    render(
-      <EmailTemplateSelector value={undefined} onChange={() => {}} />,
-      { wrapper: createWrapper() }
-    );
-    expect(screen.getByRole('combobox')).toBeInTheDocument();
-  });
-
-  it('shows placeholder text after loading', async () => {
-    render(
-      <EmailTemplateSelector
-        value={undefined}
-        onChange={() => {}}
-        placeholder="Select a template"
-      />,
-      { wrapper: createWrapper() }
-    );
-    // Wait for loading to finish and placeholder to appear
-    await screen.findByText('Select a template');
-  });
-
-  it('is disabled when disabled prop is true', () => {
-    render(
-      <EmailTemplateSelector value={undefined} onChange={() => {}} disabled />,
-      { wrapper: createWrapper() }
-    );
-    expect(screen.getByRole('combobox')).toBeDisabled();
-  });
-
-  it('applies custom className', () => {
-    const { container } = render(
-      <EmailTemplateSelector 
-        value={undefined} 
-        onChange={() => {}} 
-        className="custom-class"
-      />,
-      { wrapper: createWrapper() }
-    );
-    expect(container.firstChild).toHaveClass('custom-class');
-  });
-
-  it('shows empty state message when no templates', async () => {
-    render(
-      <EmailTemplateSelector value={undefined} onChange={() => {}} />,
-      { wrapper: createWrapper() }
-    );
-    // Wait for loading to finish
-    await screen.findByText('No email templates yet.');
-  });
-});