test: skip stale Redis status entries

[chico10117]

Summary

• make bridge-operation status scans skip Redis set members whose operation record has already disappeared
• return a clear error for unknown status names instead of scanning an empty Redis key
• add miniredis-backed regression tests for stale status-set members and unknown statuses

Validation

• go test ./redis
• go test ./...
• git diff --check

Supports the testing/reliability goals in #3.

Preferred payout if accepted: USDC on Base / EVM wallet 0x820a7bf90d944bb26bfD9b62Ab172Fc3A0829cB9.