test: standardize naming conventions to snake_case

- Rename demo_event_id → testing_event_id (more explicit)
- Rename demo_account_id → testing_account_id (matches convention)
- Rename demo_badge_id → event_badge_id (descriptive)
- Rename demo_template_id → event_badge_template_id (explicit)
- Update all test files for consistency (15 files)
- Enhance README with organized test data sections
- Update person IDs to match README test data
- No regression: 15 tests passing, 7 pre-existing failures unchanged

tests/private_network.test.ts

@@ -62,7 +62,7 @@ test('detect private/local network requests and PNA preflights', async ({ page }
         // CDP not available in this context; continue with high-level capture
     }
 
-    await page.goto('http://demo.localhost:5173/');
+    await page.goto('http://demo.localhost:5173/'); // Per README test data
     await page.waitForLoadState('networkidle');
 
     // Report findings for easier debugging