Show loading indicator on file assembling

[Koc]

Background: We've started using s3 storage instead of local files. And it performs much slower comparing to local filesystem. Now when we upload large file it can took up to 30 seconds for merging chunks into a single file. The problem is there is no any indicator of this activity and users can't understand what happening between progress bar hide and file appears in list.

You can observe how it works after the patch on the video below:

https://github.com/user-attachments/assets/7d8632f5-e06e-4f7c-9409-61cc34c67b29

[codecov[bot]]

Bundle Report

Changes will increase total bundle size by 1.47kB (0.19%) :arrow_up:. This is within the configured threshold :white_check_mark:

Detailed changes

| Bundle name | Size | Change | | ----------- | ---- | ------ | | @nextcloud/upload-esm | 382.87kB | 694 bytes (0.18%) :arrow_up: | | @nextcloud/upload-esm-cjs | 386.32kB | 780 bytes (0.2%) :arrow_up: |

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 72.72727% with 6 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@19aa6bd). Learn more about missing BASE report. Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/uploader.ts	70.58%	5 Missing :warning:
lib/components/UploadPicker.vue	80.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1458 +/- ## ======================================= Coverage ? 28.94% ======================================= Files ? 14 Lines ? 1513 Branches ? 49 ======================================= Hits ? 438 Misses ? 1075 Partials ? 0 ```

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[skjnldsv]

Hey, thanks for the PR! Unfortunately, design wise, adding some text to tell the user about the assembly is not acceptable.

Imho, to simplify this, we should :

• keep the progress bar active (if we don't do this already)
• show a new status Processing... only if there is no other upload ongoing (if the only async tasks left are move requests). If there is still some upload ongoing, they are more important than a MOVE request ongoing in the background