5251 remove enable packs

[yahyaelganyni1]

Resolves #5251

Description

This change removes the Flipper feature flag for "enable packs" since the feature is now permanently enabled in production. The work involves:

• Removing all Flipper checks for "enable_packs" throughout the codebase
• Cleaning up related conditional code paths
• Updating tests to remove mock Flipper enable_packs configurations
• Ensuring the code works correctly without the feature flag
• Removing any now-defunct code related to the packs feature flag

Type of change

• Technical debt cleanup (removing feature flag for permanently enabled feature)

How Has This Been Tested?

• All existing unit tests have been updated to remove Flipper enable_packs mocks
• Manual testing of pack-related functionality:
  • Creating requests with packs
  • Managing distributions with packs
  • Organization pack management
  • Item pack configuration
• Verified behavior works consistently without feature flag checks

Screenshots

N/A (backend changes only)

[cielf]

This is going to take a couple of sessions to do the functional check -- we basically have to check every packs-related thing (and there are a lot of them)

[yahyaelganyni1]

I understand, please let me know if I need to change anything.

[cielf]

Looks good to me -- over to @dorner for technical insight.