fix(L1): validate Nitro validator address

[leopoldjoy]

Summary

• reject a zero NITRO_VALIDATOR when deploying TEEProverRegistry
• bump the registry patch version to 0.6.1 and regenerate ABI/semver snapshots
• use nonzero mock validators in no-Nitro development and test deployments while retaining SystemDeploy validation coverage

Addresses internal audit finding L-01.

Testing

• just test (1,207 passed, 1 skipped)
• just test --match-path test/L1/proofs/TEEProverRegistry.t.sol
• just test --match-path test/L1/proofs/TEEVerifier.t.sol
• just test --match-path test/deploy/SystemDeploy.t.sol
• just lint
• just snapshots

Baseline note

just pre-pr is currently blocked by a lite-profile stack-too-deep error while compiling test/deploy/SystemDeploy.t.sol; the same failure reproduces on origin/main.

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1