fix(tests): resolve 43 regressions caused by layout.css import in test-setup

Importing layout.css in test-setup.ts activated Tailwind's responsive
breakpoint classes (hidden lg:flex, hidden md:block, etc.), making
42 elements invisible at the default narrow Playwright test viewport.

Revert the CSS import. Instead, add inline style attributes to the three
components whose tests measure computed properties (min-height, font-size)
— these values match what the Tailwind classes produce, so the real app
appearance is unchanged.

Also fix goto mock leakage in the geschichten/[id] delete-failure test:
the delete-success test's goto('/geschichten') call was not cleared before
the failure test ran. Add beforeEach(vi.clearAllMocks) to reset mock state.

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

frontend/src/routes/geschichten/[id]/page.svelte.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, afterEach } from 'vitest';
+import { describe, it, expect, vi, afterEach, beforeEach } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
 import { page, userEvent } from 'vitest/browser';
 
@@ -28,6 +28,9 @@ import type { components } from '$lib/generated/api';
 const { default: GeschichtePage } = await import('./+page.svelte');
 
 afterEach(cleanup);
+beforeEach(() => {
+	vi.clearAllMocks();
+});
 
 type GeschichteView = components['schemas']['GeschichteView'];