web: improve ProgressBackdrop tracking API and its look & feel

[dgdavid]

Tracking API

Use a single options object to configure progress backdrop behavior, instead of passing multiple loosely related props through consumers.

- <Page progressScope="storage" additionalProgressKeys={STORAGE_MODEL_KEY}>
+ <Page progress={{ scope: "storage", ensureRefetched: STORAGE_MODEL_KEY }}>

Look and feel

The progress message is now always visible, even if the user had previously scrolled the content before the progress appeared.

Before	After

Legibility has been improved by increasing the text size and using a gray overlay background from the SUSE brand palette. Although we initially kept the default PF Backdrop background to provide immediate visual feedback about the blocked content area, this feedback is already sufficiently conveyed by the blurred content underneath.

Progress actions are expected to be short-lived; if they do take longer, users can still clearly perceive that interaction is blocked, while benefiting from significantly improved text readability (black on gray instead of black on near-black).

Before	After

[imobachgs]

It looks better now, thanks!

[dgdavid]

It looks better now, thanks!

Thanks Imo!

Please, excuse me. I have extended a bit the PR since I didn't realize this was already approved. Do you mind have another look?

[dgdavid]

The idea here is to use a Tagged type, similar to what was already done for
TranslatedString. This would allow queries to export their keys as a QueryKey (or similar), enabling the compiler to verify that valid values are provided to the ensureRefetched prop.