PM-34085: Chore: Remove the Authenticator Sync backwards compatibility

[david-livefront]

🎟️ Tracking

PM-34085

📔 Objective

This PR removes the backwards compatibility of the Authenticator Sync in order to clear up the implementation. This changes means that in order for the sync functionality to work properly both the Password Manager and Authenticator must be running v2026.4.0 or later.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.29%. Comparing base (fce814d) to head (37208c2).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...tor/repository/util/SharedAccountDataExtensions.kt	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6928      +/-   ##
==========================================
- Coverage   86.33%   86.29%   -0.05%     
==========================================
  Files         873     1000     +127     
  Lines       63483    65877    +2394     
  Branches     9200     9251      +51     
==========================================
+ Hits        54808    56847    +2039     
- Misses       5514     5842     +328     
- Partials     3161     3188      +27     

Flag	Coverage Δ
app-data	17.22% <0.00%> (+0.15%)	⬆️
app-ui-auth-tools	19.43% <0.00%> (+0.29%)	⬆️
app-ui-platform	16.96% <0.00%> (+0.58%)	⬆️
app-ui-vault	28.48% <0.00%> (+0.57%)	⬆️
authenticator	6.24% <0.00%> (-0.01%)	⬇️
lib-core-network-bridge	4.08% <50.00%> (+<0.01%)	⬆️
lib-data-ui	1.15% <0.00%> (+<0.01%)	⬆️

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[aj-rosado]

LGTM

[david-livefront]

Thanks @aj-rosado