Add Playwright automation aids for disclaimer and modals

- Added `data-testid` attributes to key modals (Disclaimer, Login, Upload, Video, Profile, Lockdown) to facilitate reliable selection in Playwright tests.
- Updated `js/disclaimer.js` and `js/index.js` to respect a new `playwright-bypass-disclaimer` localStorage flag, allowing automated tests to skip the disclaimer modal entirely.

components/lockdown-modal.html

@@ -6,6 +6,7 @@
   aria-labelledby="lockdownModalTitle"
   aria-describedby="lockdownModalDescription"
   data-ds="new"
+  data-testid="lockdown-modal"
 >
   <div class="bv-modal-backdrop"></div>