Add helper for computing bonding curve price at any given supply step without mutating contract state

[Chucks1093]

Summary

Computing the expected price for a given supply step requires running the same formula used in the buy/sell path. A pure helper function should expose this calculation so tests and off-chain tooling can predict prices without invoking a state-mutating transaction.

Scope

• Add a read-only query_price(supply: u64) -> i128 contract function
• Must return the same value the buy function would compute for that supply step
• Should not require admin authentication
• Add unit tests for supply 0, supply 1, and a mid-range supply value confirming the result matches the inline formula

Acceptance Criteria

• query_price is read-only and requires no auth
• Returns the same value as the buy-path formula for the same supply
• Unit tests pass for supply 0, 1, and mid-range
• No storage reads or writes occur during the call

ETA: 12 hours

---

Coordinate on Telegram

[OluRemiFour]

I can take this on. I've gone through the details and will provide a well-tested solution aligned with the project standards.

[Killerjunior]

Can I work on this?

[Babigdk]

Hi Maintainer! I'd like to work on this issue if it becomes available.

I have experience developing and testing Soroban smart contracts and mathematical pricing logic. I'll implement a pure query_price(supply: u64) -> i128 function that reuses the existing bonding-curve calculation to ensure it always matches the buy-path formula without mutating contract state or requiring authorization. I'll also add focused unit tests for supply 0, 1, and a representative mid-range value, verifying that the helper returns identical results to the buy calculation while performing no storage reads or writes.