Verify dest transaction sender matches miner's posted address

[LandynDev]

Verify dest transaction sender matches miner's posted address

Summary

• Security fix: The dest-side swap verification only checked that the correct amount reached the user's address by tx hash — it did not verify the transaction came FROM the miner's posted address. A miner could watch for any third-party tx to the user's dest address of the correct amount and claim that tx hash as their fulfillment without actually sending funds.
• Contract: Added miner_dest_address field to SwapData
• Validator: chain_verification.py now validates tx_info.sender against swap.miner_dest_address on the dest leg, rejecting mismatches

Test plan

• cargo contract build compiles with new field
• ruff check allways/ neurons/ passes
• Restart dev environment and run E2E suite 02 (swap lifecycle)
• Verify validator logs show sender validation on dest-side confirmation

[plind-dm]

What is it for? Specifically for which issue?