feat: Use a local cache (storage) for front pictures

[g123k]

Hi everyone!

This PRs introduces cached_network_image as a dependency.
It allows to cache locally images.

For now, only front pictures use this mechanism.
To test:

• Is-it better?
• Should we increase the size of the cache?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 6.20%. Comparing base (4d9c7fc) to head (cd81c98).
Report is 666 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ckages/smooth_app/lib/database/transient_file.dart	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #6217      +/-   ##
==========================================
- Coverage     9.54%   6.20%   -3.35%     
==========================================
  Files          325     456     +131     
  Lines        16411   26703   +10292     
==========================================
+ Hits          1567    1656      +89     
- Misses       14844   25047   +10203     

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[monsieurtanuki]

Hi @g123k!
Good idea!
It would probably be better if we could already have an explicit control on the cache parameters - instead of using blindly the default values.
For instance, our front images never stale.
And we may use different parameters for different kinds of images:

• most important being front x thumbnails - here we can store a lot
• front x full - here we may store less as they are much bigger

[g123k]

The reason for my comment to decide later about the cache is:

• 1. There are improvements vs the situation today
• 2. The cache is not based on the size on the storage, but the number of files.

The lib is based on flutter_cache_manager, where we can only set:

static CacheManager instance = CacheManager(
    Config(
      key,
      stalePeriod: const Duration(days: 7),
      maxNrOfCacheObjects: 20,
      repo: JsonCacheInfoRepository(databaseName: key),
      fileSystem: IOFileSystem(key),
      fileService: HttpFileService(),
    ),
  );

[monsieurtanuki]

@g123k That's my point - using default values may not be suitable in our case:

• stalePeriod: const Duration(days: 7) - we don't have stale periods
• maxNrOfCacheObjects: 20 - could be ok, but it will consider both front thumbnails and front full images

If those default values are what you were targetting, that's perfect actually.