Add keeper claim handler and tests

[Pray4Lovee]

Summary

• route MsgClaim messages through the EVM keeper so claim requests move funds to the associated Sei address
• add keeper implementation that transfers all native balances from the sender to the claimer
• cover the new flow with tests for successful, empty, and invalid claim scenarios

Testing

• go test ./... (fails: toolchain download blocked by environment restrictions)

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https://chatgpt.com/codex/tasks/task_e_68d0543dc4b48322a3e0960fdaa127f9