[14.0][FIX] account_asset_transfer_extension: prevent deletion of AUC transfer moves

[eantones]

Summary

• Prevent unlink_move() from deleting AUC transfer moves (CURS journal entries) when a user clicks "unpost" on a to_asset's init_entry depreciation line
• The bug caused the CURS move to be permanently deleted, leaving from_assets with transfer_move_id = NULL and the revert wizard showing "Nothing to revert"
• Add override of unlink_move() on account.asset.line that raises UserError if the move is referenced by transfer_move_id on any asset

Test plan

• Create a transfer (AUC → final assets) via the transfer wizard
• Open a to_asset, go to depreciation board, try to "unpost" the init_entry (type=create) line
• Verify that a UserError is raised with the message directing to use "Revert Transfer" instead
• Verify that normal depreciation lines can still be unposted without issues
• Verify that the "Revert Transfer" wizard still works correctly

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.62%. Comparing base (b45d2b3) to head (33f8a3d).
⚠️ Report is 4 commits behind head on 14.0.

Files with missing lines	Patch %	Lines
...et_transfer_extension/models/account_asset_line.py	45.45%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             14.0     #860      +/-   ##
==========================================
- Coverage   50.62%   50.62%   -0.01%     
==========================================
  Files         971      972       +1     
  Lines       16406    16418      +12     
  Branches     3496     3500       +4     
==========================================
+ Hits         8306     8312       +6     
- Misses       7887     7893       +6     
  Partials      213      213              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.