Fix migrationConfigs map not propagated during account update

[nicolaslopezbravo]

Summary

• AccountInfoMap.addOrUpdateAccounts() was copying migrationConfig (singular) but not migrationConfigs (the fabric-specific map) when merging an incoming account update with an existing account.
• This caused updates to the migrationConfigs map to be silently dropped since the builder retained the old account's value.
• Added the missing .migrationConfigs(account.getMigrationConfigs()) call in the builder chain.

Testing Done

• Added migrationConfigs test counterparts for every existing migrationConfig test (account-level):

File	Test	Covers
InMemoryAccountServiceTest	updateAccountMigrationConfigs	Update: change map, verify new keys present and old keys removed
InMemoryAccountServiceTest	updateAccountClearMigrationConfigs	Delete: set to null, verify cleared
MySqlAccountServiceTest	testAccountMigrationConfigsPersistence	Create, update, and delete through MySQL mock path
MySqlAccountServiceTest	testLegacyAccountJsonDeserialization	Assert migrationConfigs is null for legacy JSON
MySqlAccountServiceIntegrationTest	testAccountMigrationConfigsIntegration	Create, update, and delete end-to-end
MySqlAccountServiceIntegrationTest	testAddMigrationConfigsToExistingAccount	Add migrationConfigs to account created without them

• All unit tests pass. Integration tests compile successfully.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.81%. Comparing base (52ba813) to head (75e91be).
⚠️ Report is 345 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3201      +/-   ##
============================================
+ Coverage     64.24%   69.81%   +5.56%     
- Complexity    10398    12811    +2413     
============================================
  Files           840      930      +90     
  Lines         71755    79090    +7335     
  Branches       8611     9463     +852     
============================================
+ Hits          46099    55214    +9115     
+ Misses        23004    20926    -2078     
- Partials       2652     2950     +298     

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