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/upload-modal.html

@@ -7,6 +7,7 @@
   aria-labelledby="uploadModalTitle"
   aria-describedby="uploadModalDescription"
   data-ds="new"
+  data-testid="upload-modal"
 >
   <div class="bv-modal-backdrop" data-dismiss></div>