[CT-02] Implement on-chain Member Tier Calculator in Rust

[devwums]

Problem

Member tier classification exists only in the NestJS backend. The smart contract layer has no knowledge of tiers, making on-chain tier-based rewards unverifiable and gameable.

Proposed Solution

Create contracts/cntr/member_tier.rs defining #[derive(Debug, PartialEq, Clone)] pub enum MemberTier { Bronze, Silver, Gold, Platinum } and implementing pub fn calculate_tier(total_bookings: u32, total_spend_stroops: i128) -> MemberTier. Tier thresholds (either condition triggers upgrade): Bronze = default, Silver = 10+ bookings OR 5,000,000 stroops, Gold = 30+ OR 20,000,000 stroops, Platinum = 100+ OR 100,000,000 stroops. All implementation must live inside contracts/cntr/.

Acceptance Criteria

• File at contracts/cntr/member_tier.rs
• MemberTier enum derives Debug, PartialEq, Clone
• All 4 tiers are reachable via the function
• Boundary conditions correct (e.g., exactly 10 bookings returns Silver)
• At least 8 unit tests in a #[cfg(test)] block
• Compiles with cargo test

[Samaro1]

@Samaro1 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Gm gm boss, I would love to work on this issue. A satisfactory PR will be raised in 8 hours tops

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[Userhorlie]

@Userhorlie has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I would love to take on this issue.

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[Userhorlie]

Resolved in PR #1044. Implementation lives in contracts/cntr/ with all acceptance criteria met and tests passing.

[Userhorlie]

Implemented in PR #1044. All acceptance criteria met, 26 unit tests passing.

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