feat: 3897 - no language selector for gallery, only for swipeable page

[monsieurtanuki]

What

• This PR brings consistency about multilingual images, in read AND write.
• The carousel and the gallery images now match the app language.
• In the swipeable page, you have a language selector and you now see actual multilingual images:
  • an image uploaded for that language
  • or an empty image with a "no image for that language yet" label
  • or an empty image with a "no image" label (in any language)

Screenshot

App in French

gallery	swipeable with image

swipeable with no image / language	swipeable with no image at all

Fixes bug(s)

• Closes: Multilingual images #3897

Files

Main changes:

• app_en.arb: added 2 translations ("no image" / "no image for that language")
• app_fr.arb: added 2 translations ("no image" / "no image for that language")
• nutrition_page_loaded.dart: removed an implicit language parameter
• product_cards_helper.dart: refactoring
• product_image_gallery_view.dart: removed the language selector
• product_image_swipeable_view.dart: removed the language parameter; now we always start with the app language
• product_image_viewer.dart: now always displays the (non) image for the specified language, with additional labels; added explicit language parameters
• transient_file.dart: new method getImageLanguages

Added explicit language parameters for:

• add_new_product_page.dart
• background_task_crop.dart
• background_task_image.dart
• background_task_unselect.dart
• edit_ingredients_page.dart
• edit_new_packagings.dart
• image_crop_page.dart
• image_upload_card.dart
• new_crop_page.dart
• product_image_local_button.dart
• product_image_server_button.dart
• uploaded_image_gallery.dart

[codecov-commenter]

Codecov Report

Merging #3924 (42552b3) into develop (558034f) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           develop    #3924      +/-   ##
===========================================
- Coverage    10.63%   10.62%   -0.01%     
===========================================
  Files          268      268              
  Lines        13494    13506      +12     
===========================================
  Hits          1435     1435              
- Misses       12059    12071      +12     

Impacted Files	Coverage Δ
...mooth_app/lib/background/background_task_crop.dart	0.00% <0.00%> (ø)
...ooth_app/lib/background/background_task_image.dart	0.00% <0.00%> (ø)
...h_app/lib/background/background_task_unselect.dart	0.00% <0.00%> (ø)
...th_app/lib/cards/data_cards/image_upload_card.dart	0.00% <0.00%> (ø)
...ckages/smooth_app/lib/database/transient_file.dart	0.00% <0.00%> (ø)
.../smooth_app/lib/helpers/image_field_extension.dart	0.00% <0.00%> (ø)
...s/smooth_app/lib/helpers/product_cards_helper.dart	0.00% <0.00%> (ø)
...th_app/lib/pages/image/uploaded_image_gallery.dart	0.00% <0.00%> (ø)
packages/smooth_app/lib/pages/image_crop_page.dart	0.00% <ø> (ø)
...th_app/lib/pages/product/add_new_product_page.dart	0.00% <0.00%> (ø)
... and 9 more

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[teolemon]

👌

[monsieurtanuki]

Thank you @teolemon for your review!
I think this time the interface is consistent.

There's still a minor bug when you unselect an image that you just added (it's not taken into account immediately), that I'm about to fix. The bug was already there before the multilingual feature.