Add `referral` CLI command

[Levi-Ojukwu]

Description:

The contract tracks referral counts per referral code (at lib.rs:915-920). When a freelancer submits an invoice with a referral code, the count for that code is incremented. The CLI has no command to query these counts.

The CLI command should:

• Accept --code (required) — hex-encoded 32-byte referral code
• Display the referral count

Why it matters: Referrers need to track their performance.

Acceptance Criteria:

• Create cli/src/commands/referral.ts
• Accept --code parameter (hex string)
• Validate code format (64 hex characters)
• Display referral count
• Register in cli/src/index.ts as iln referral

Relevant Files: contracts/invoice_liquidity/src/lib.rs:915-920, cli/src/index.ts

---

[nazteeemba]

Please assign me to this issue

[Robotron2]

I'd like to work on this issue.

I'll add a new iln referral CLI command that accepts a required --code argument, validates it as a 32 byte hex value, and queries the contract for the associated referral count. I'll also register the command in the CLI entry point and ensure the output is clear and consistent with the existing command structure.

I've worked on TypeScript CLIs and blockchain tooling, so I'm comfortable implementing this while keeping it aligned with the project's current patterns. I should be able to have a tested PR ready within a day.

[grantfox-oss]

🦊 GrantFox — @Robotron2 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #421)
2. Your PR will be reviewed by the Invoice-Liquidity-Network maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@Robotron2's PR #504 was approved and merged by @Nursca.

🏆 @Robotron2: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (554 total points). Track your full progress on GrantFox.

👏 Great work, @Robotron2! Keep contributing to Invoice-Liquidity-Network.