Add faucet-usage metrics event so ops can monitor testnet consumption

[thlpkee20-wq]

Description

Expose faucet_metrics_v1 events that emit periodically summarizing total dispensed, unique addresses served, and recent cooldown rejects. Enables ops dashboards.

Requirements and context

• Must be secure, tested, and documented
• Should be efficient and easy to review
• Relevant code: src/test_faucet_seed.rs, indexer/
• Metrics must be idempotent per emission window

Suggested execution

• Fork the repo and create a branch
• git checkout -b feat/faucet-metrics-event
• Implement changes
  • Add faucet_metrics_v1 topic emitter
  • Emit on schedule keyed to ledger time
  • Add indexer fixture
• Validate security and correctness assumptions

Test and commit

• Run tests
  • cargo test --all
• Cover edge cases
  • Two emissions within the same window (dedup)
• Include test output and security notes

Example commit message

feat: emit faucet_metrics_v1 events

Guidelines

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 96 hours

[Naajih09]

Hey maintainer, i have read your description and i have worked on several issues like this, kindly assign to me

[Purity-Euphemia]

Good Day Maintainer, I have experience and would review the issue, implement a clean solution, test it, and submit a pull request.