fix: correct not available on web tooltip

[kp-krish]

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Closes #1827

The not_available_web snackbar was missing a separator and read Not available use the web version. This updates it to Not available - use the web version, matching the wording of the neighbouring coming_soon_web string (Coming soon - use the web version).

The string is shown by disabledButtonSnack() in lib/ui/views/learn/landing/landing_viewmodel.dart when a curriculum item is web-only.

The same correction is applied to app_es.arb and app_pt.arb, which both carry the untranslated English string, along with the corresponding generated localization files.

Verified locally on Flutter 3.44.9 (the version pinned in CI):

• flutter pub get regenerates the localization files with no further diff, so the committed generated output matches gen-l10n exactly
• flutter analyze --no-fatal-warnings reports no new issues
• flutter test unit and flutter test services pass

[Nirajn2311]

Could you manually do the same change for the other languages as well. As of now Crowdin is not used

[kp-krish]

Thanks for the review, and for clarifying that Crowdin isn't in use right now.

I've applied the same correction to app_es.arb and app_pt.arb plus their generated files. Both locales currently hold the untranslated English string for this key (in fact all 300 keys in both files are still identical to the English source), so I mirrored the English wording rather than introducing a Spanish or Portuguese translation for this one string alone. Happy to add real translations instead if you'd prefer.