[contract] Add 3 Tests to liquidity_tests.rs (Part 1)

[Olowodarey]

📋 Overview

Expand test coverage for the liquidity module by adding 3 new tests (Part 1 of 2).

✅ Tasks

• Add 3 new test functions to contract/tests/liquidity_tests.rs
• Follow existing test patterns and helper functions
• Verify all tests pass

🧪 New Tests (3 total)

Test 1: Add Liquidity Creates Pool

#[test]
fn test_add_liquidity_creates_pool() {
    // Create market
    // Add liquidity (first provider)
    // Verify pool is created with correct reserves
    // Verify LP tokens are minted
}

Test 2: Remove Liquidity Burns Tokens

#[test]
fn test_remove_liquidity_burns_tokens() {
    // Add liquidity
    // Remove liquidity
    // Verify LP tokens are burned
    // Verify funds are returned
}

Test 3: Swap Updates Reserves

#[test]
fn test_swap_updates_reserves_correctly() {
    // Add liquidity
    // Perform swap
    // Verify reserves are updated according to constant product formula
}

🔍 Verification

• All 3 tests written
• All tests pass
• Tests follow existing patterns
• No clippy warnings

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