refactor: remove dedicated redemption contract datum decoding

[ozgb]

Overview

Redemption UTxOs already have the correct stake credentials in their address, so the dedicated redemption queries (which decode datums) are unnecessary. The standard asset_create/asset_spend queries catch redemption UTxOs via their cNIGHT policy ID.

We have performed limited testing on redemption UTXO observation - removing this code improves our test coverage.

Includes a v0→v1 storage migration that clears UtxoOwners and resets NextCardanoPosition to trigger a full replay from genesis.

Redemption contract analysis

The Redemption validator enforces that the continuing UTxO preserves its staking credential across thaws. On-chain verification of all 7,601 unspent Redemption UTxOs (as of 25/12/25) confirms:

• 0 mismatches between address staking credential and datum staking credential
• Only 111 out of 7,601 redemption UTxOs (1.46%) use enterprise addresses with no staking credential — these are correctly handled by the existing asset queries
• 3 UTxOs have no inline datum (edge cases)

Contract	Payment Credential	Address Type
RedemptionSupply	9015199b...	Enterprise script (addr1w) — single address
Redemption	5986bfcc...	Base script+keyhash (addr1z) — one per user

The Redemption script's thaw validator (Terms.hs:211) enforces:

(outAddress == Address (ScriptCredential ownHash) stakingCredential)                                       

This means the delegation part of the UTxO address is preserved across thaws, so address-based queries are reliable without datum decoding.

🗹 TODO before merging

• Confirm the percentage of stake-less redemption UTxOs is still small with latest db-sync snapshot
• Ensure we have a clean path to upgrade
• Ready

📌 Submission Checklist

• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason:
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• Updated AGENTS.md if build commands, architecture, or workflows changed
• No new todos introduced

🧪 Testing Evidence

Please describe any additional testing aside from CI:

• Additional tests are provided (if possible)

🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other:
• N/A

Links

[github-actions]

KICS version: v2.1.16

Category Results CRITICAL 0 HIGH 0 MEDIUM 94 LOW 12 INFO 83 TRACE 0 TOTAL 189	Metric Values Files scanned 28 Files parsed 28 Files failed to scan 0 Total executed queries 73 Queries failed to execute 0 Execution time 6