fix(vara.eth): reject post-quarantine-delay above 1000

[neelsatyavolu]

Closes #5478

Summary

Root cause: post_quarantine_delay was accepted at any u32 value. The producer walks canonical_quarantine + post_quarantine_delay parents through the database on every wait_for_proposable_content call. A typo such as --post-quarantine-delay 4294967295 therefore turned each call into millions of RocksDB reads, and nothing told the operator.

Fix: follows the plan in the issue.

• Add MalachiteServiceConfig::MAX_POST_QUARANTINE_DELAY = 1000 and drop the TODO: #5478 comment it replaces.
• NodeParams::into_config now fails with `post-quarantine-delay` must be at most 1000, got N. The check runs on the effective value, so it covers both the CLI flag and the TOML key.
• The --post-quarantine-delay help text now mentions the maximum.

How to test

cargo test -p ethexe-cli --lib params::node::tests

• post_quarantine_delay_above_max_is_rejected checks that 1001 is rejected with an error naming the option. I wrote it before the fix and confirmed it failed on master: into_config() returned a NodeConfig with post_quarantine_delay: 4294967295.
• post_quarantine_delay_at_max_is_accepted checks that 1000 is still accepted.

Also ran locally on macOS (arm64):

• cargo test -p ethexe-cli -p ethexe-malachite: all pass.
• cargo clippy -p ethexe-cli -p ethexe-malachite --all-targets -- -D warnings: clean.
• cargo fmt --all -- --check: clean.

Notes

• I didn't run make typos locally because typos-cli isn't installed here.
• Unrelated to this change: on macOS 27 with Apple clang 21, sha1-asm 0.5.3 (pulled in through gear-workspace-hack) fails to build. The Xcode clang crashes on its #:lo12: relocation syntax in aarch64_apple.S. To run the checks above I passed a local [patch] through cargo --config. That workaround is not part of this PR.
• This PR was written with the help of an AI agent (Claude Code, claude-opus-5-5). Per CONTRIBUTING.md, it probably qualifies for the ai-generated label, but I can't set labels on this repository.

Checklist

• PR title follows Conventional Commits (type(scope): description)
• Single logical change
• Tests added or updated (if logic changed)
• Docs updated (if needed)