[PM-26960] chore: Remove forceUpdateKdfSettings feature flag

[matt-livefront]

🎟️ Tracking

PM-26960

📔 Objective

Removes the forceUpdateKdfSettings (pm-18021-force-update-kdf-settings) feature flag.

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

Reviewed the removal of the forceUpdateKdfSettings (pm-18021-force-update-kdf-settings) feature flag. The change removes the flag enum case and its CaseIterable entry, drops the two flag guards inside ChangeKdfService.needsKdfUpdateToMinimums() and updateKdfToMinimums(), and updates the DI wiring and tests accordingly. The behavior previously gated by the flag is now always enabled, which matches the intent of the flag removal; the underlying KDF eligibility guards (PBKDF2 type, iterations below minimum, master password present) remain intact, and no references to the removed flag remain in the codebase.

Code Review Details

No blocking findings.

Minor (non-blocking, not posted inline): the test docstring at BitwardenShared/Core/Auth/Services/ChangeKdfServiceTests.swift:121 still reads "returns true if the feature flag is on...", which is now stale since the flag is gone. Optional cleanup.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.82%. Comparing base (66a5f60) to head (9ff3dcb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2799      +/-   ##
==========================================
+ Coverage   80.80%   80.82%   +0.02%     
==========================================
  Files        1019     1019              
  Lines       64854    64847       -7     
==========================================
+ Hits        52404    52412       +8     
+ Misses      12450    12435      -15     

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