test: fix video modal tests and add missing polyfills

- Added `scrollTo`, `HTMLMediaElement.prototype.pause`, and `load` polyfills in `tests/video-modal-accessibility.test.mjs` (via `setupModal`) and `tests/test-setup.mjs`.
- Added defensive check in `ModalManager.teardown` to prevent `TypeError` when removing event listeners.
- Updated `tests/video-modal-moderation.test.mjs` to use correct selector `[data-moderation-bar]` and updated assertions for moderation overlay visibility (override state).
- Created `tests/test-setup.mjs` to handle early global polyfills for dependencies like `floating-ui`.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/ui/ModalManager.js

@@ -705,10 +705,12 @@ export default class ModalManager {
 
     if (this.uploadModal && this.uploadSubmitHandler) {
       try {
-        this.uploadModal.removeEventListener(
-          "upload:submit",
-          this.uploadSubmitHandler,
-        );
+        if (typeof this.uploadModal.removeEventListener === "function") {
+          this.uploadModal.removeEventListener(
+            "upload:submit",
+            this.uploadSubmitHandler,
+          );
+        }
       } catch (error) {
         devLogger.warn("[ModalManager] Failed to remove upload submit handler:", error);
       }