feat: market token NAV price view — USD value per GM token

[abayomicornelius]

Summary

LPs and the frontend need to know the current USD price per market (GM) token to display portfolio value and compute withdrawal amounts. Add a dedicated view to reader.

Proposed API

pub fn get_market_token_price(
    env: Env,
    data_store: Address,
    oracle: Address,
    market: Address,
    maximize: bool,     // use max oracle price (for minting) or min (for burning)
) -> u128              // USD price per 1 market token, FLOAT_PRECISION scaled

Implementation Notes

• nav = get_pool_value(market, maximize) / market_token.total_supply()
• Handle zero-supply edge case (no market tokens outstanding) — return a seed price
• maximize = true uses oracle max prices (conservative for minting)
• maximize = false uses oracle min prices (conservative for burning)

Acceptance Criteria

• Returns correct NAV for a single-asset pool
• Returns correct NAV for a multi-asset imbalanced pool
• Zero-supply case returns configured seed price without panic
• Unit test: deposit 10,000 USD, supply = 10,000 GM, price = 1.00 USD
• Unit test: after 200 USD in fees, price = 1.02 USD

Affected Contracts

reader, market_utils

[Primex-hub]

@sleek007 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I will like to work on this project

ℹ️ Repo Maintainers: To accept this application, review their application or assign @sleek007 to this issue.