Add regression coverage for contract boundaries

[Ashmuk001]

Adds regression coverage and enforcement for four contract issues:

• Fees: require a prior commitment for config updates and enforce the apply timelock.
• Disputes: reject repeat council votes from the same voter.
• Monitor: verify the exact bet cap succeeds and the next bet fails.
• Validators: verify inclusive minimum and maximum stake boundaries.

Closes #202
Closes #203
Closes #205
Closes #207

Validation: git diff --check passed. Rust tests could not be run because cargo is unavailable in the environment.

[drips-wave]

@Ashmuk001 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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