Port the bitstream-name-in-upload-notifications feature to dtq-dev-9

[milanmajchrak]

Follow-up to #1411 (UoE/Bitstream name in upload notifications), which deliberately targets dtq-dev only.

dtq-dev-9 needs the same feature as a third, separate PR — and it is not a cherry-pick, because that branch is the vanilla-equivalent shape, not the CLARIN one:

• zero size-limit code — dtq-dev-9 has no onWhenAddingFileFailed handler, so onUploadError there is the plain upstream one. None of UoE/Bitstream name in upload notifications #1411's AC-D-04 discriminator work applies, and none of it should be carried over.
• BOTH template bindings change, not one. On dtq-dev the template already passes $event to onUploadError; on dtq-dev-9 (like vanilla main) it does not, so (onUploadError)="onUploadError()" → (onUploadError)="onUploadError($event)" is required or the error half of the feature ships dead while looking complete.
• strictTemplates must be checked on that branch before coding. It was verified NOT set on dtq-dev and on vanilla main; if dtq-dev-9 enables it, the retyped onUploadError: EventEmitter<UploaderError> binding needs re-checking.
• The theme wrapper on dtq-dev-9 delegates to the core template, so no themed file is involved.

The three frozen decisions from #1411 apply unchanged: output identifier onCompleteItemWithFile, producer-strict isNotEmpty(fileName) (empty names omit the key), and the default interpolate param for missing translations.

The prepared vanilla-equivalent patch that dtq-dev-9 should follow is in this working set as work/patches/vanilla.patch.

[milanmajchrak]

Closing — filed outside the agreed scope of #1411. The content is preserved in that PR's working notes if we want to re-file it deliberately later.