fix: DoS protection, input sanitization, and dependency vulnerability scanning #1

[Spagero763]

Summary

• DoS protection (dos_protection.rs): Introduces a dedicated module with batch-size constants, instruction-budget guards, check_batch_size, check_instruction_budget, check_bridge_out_rate_limit, and a new check_admin_rate_limit to throttle back-to-back bulk admin operations. emergency.rs now enforces these guards on pause_chains and resume_chains.
• Input sanitization (validation.rs): Fixes the wrong error variant in validate_characters (was InvalidStringLength, now correctly InvalidCharacters). Adds the InvalidCharacters variant to ValidationError, a trim_and_validate helper that strips ASCII whitespace before checking length and character set, and InputSanitizer::sanitize_string as the recommended entry-point for user-supplied string fields.
• Dependency scanning (ci.yml, dependabot.yml, deny.toml): Adds a security-audit CI job that runs cargo audit and cargo deny on every push/PR. Adds Dependabot configuration for weekly Cargo and GitHub Actions dependency update PRs.

Test plan

• Confirm cargo audit and cargo deny check pass in the new CI job
• Verify pause_chains / resume_chains reject calls that exceed MAX_CHAIN_BATCH_SIZE with BatchSizeLimitExceeded
• Verify pause_chains / resume_chains reject rapid back-to-back admin calls with RetryBackoffActive
• Verify validate_characters returns InvalidCharacters (not InvalidStringLength) for disallowed bytes
• Verify trim_and_validate strips leading/trailing whitespace before applying the length cap
• Confirm Dependabot PRs are opened on the weekly schedule

closes #233
closes #260
closes #276

[drips-wave]

@Spagero763 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! 🚀

Learn more about application limits

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[Spagero763]

kindly merge @RUKAYAT-CODER i have solved alot of pipeline errors

[Spagero763]

@RUKAYAT-CODER kindky merge PR