fix(wstaking): allow historical fixed deposit migration rates

[modelsbridgeaicom-ship-it]

Fixes #933.

Summary

• keeps migrated fixed deposits on their stored historical rate and interest instead of requiring the destination region's current config rate to match
• requires only that the destination region still has an active config for each migrated fixed-deposit term
• adds a focused regression test for historical-rate mismatch plus missing/inactive term rejection

Tests

• Passed: git diff --check
• Attempted: ..\..\tools\go\bin\go.exe test .\x\wstaking\keeper -run TestValidateTransferFixedDepositCfg -count=1 -v
  • Blocked by existing upstream dependency compile error in github.com/openmetaearth/ethermint/app/ante/eip712.go: missing secp256k1.RecoverPubkey and secp256k1.VerifySignature.
• Attempted: ..\..\tools\go\bin\go.exe test .\x\wstaking\types -count=1
  • Blocked by existing MsgIbcTransferFromRegionTreasure fixture failures with blank IBC port/channel identifiers.