Add property-based tests asserting the slippage protection invariant and cooldown guard across random inputs

[Chucks1093]

Summary

The slippage protection and cooldown guard involve comparison logic that must hold for all valid input combinations. Property-based tests with randomised prices, quantities, and ledger numbers should assert these invariants never silently fail.

Scope

• Generate random (execution_price, max_price) pairs and assert SlippageExceeded is raised iff execution_price > max_price
• Generate random (execution_price, min_price) pairs and assert SlippageExceeded is raised iff execution_price < min_price
• Generate random (last_buy_ledger, current_ledger, cooldown) triples and assert CooldownActive is raised iff current_ledger - last_buy_ledger < cooldown
• Run at least 10 000 iterations per property
• Log the reproducing seed on any invariant violation

Acceptance Criteria

• Slippage buy invariant holds across 10 000 random inputs
• Slippage sell invariant holds across 10 000 random inputs
• Cooldown invariant holds across 10 000 random inputs
• Reproducing seed logged on any violation
• Tests run within Soroban budget limits per iteration

ETA: 24 hours

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[Sureplus30]

@Sureplus30 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would like to work on this kindly assign me

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[matthewester2014-jpg]

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I like to work on this.

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[adelekevictor12]

@adelekevictor12 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer, i can fix this issue

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[DammyAji]

@DammyAji has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Assign me please

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