test: switch all test fixtures from japan-korea-2026 to italy-2026-demo

- Replace all japan-korea-2026 URL references in test files
- dailies.spec.js: update KNOWN_SLUG/TITLE/CITY/COUNTRY to first campiglia entry
- accessibility.spec.js: update AX4 entry URL to campiglia entry
- helpers.js: update TRACKER_DIR to italy-2026-demo dailies

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Vgmzx8VTTTmCskSpQtsLTr

tests/ui/post.spec.js

@@ -39,7 +39,7 @@ test('P1: post text-only entry → created on disk and visible on /dailies', asy
     const photos = fs.readdirSync(entryDir).filter(f => /\.(jpg|jpeg|png|webp|heic)$/i.test(f));
     expect(photos.length, 'Text-only entry should have no photos').toBe(0);
 
-    await page.goto('/trips/japan-korea-2026/dailies');
+    await page.goto('/trips/italy-2026-demo/dailies');
     await expect(page.locator('body')).toContainText(tag);
 });
 
@@ -71,7 +71,7 @@ test.skip('P2: post entry with photo → photo saved in entry folder and visible
     const photos = fs.readdirSync(entryDir).filter(f => /\.(jpg|jpeg|png|webp|heic)$/i.test(f));
     expect(photos.length, 'At least one photo should be saved').toBeGreaterThan(0);
 
-    await page.goto('/trips/japan-korea-2026/dailies');
+    await page.goto('/trips/italy-2026-demo/dailies');
     await expect(page.locator('body')).toContainText(tag);
 });