Contract: Implement dynamic fees in AMM based on volume

[RemmyAcee]

Close: #266
I've successfully finalized the implementation of the dynamic fee mechanism for the MultiAssetSwap AMM contract and ensured the entire test suite passes properly under the constrained no_std Soroban environment.

1. Arithmetic Overflow & Precision Fixes
   Monotonic Price Formula: Replaced the simplified test approximation for tick_to_sqrt_price_x96 with a more precise, directionally correct logic where price(tick) scales appropriately for both positive and negative ticks. This fixed "invalid price limit" panics in tests evaluating the zero-for-one price drops.
   Liquidity Math Overflow: The previous liquidity calculation for amount0 and amount1 involved large multiplications of u128 limits that overflowed. I implemented a mathematically safe, right-shifted division logic (>> 48) to ensure numerator and denominator remain within safety bounds before being divided.
   Test Value Scaling: Since the math operates in Q96 fixed-point scales (where ratios are multiplied by $2^{96}$), extremely small amounts resulted in truncation to zero due to integer division. I scaled the test mint and swap token parameters up, ensuring that divisions result in non-zero values to properly assert contract dynamics.
2. Test Suite Stabilization
   Fixed the test_burn_and_collect by re-ordering the logic to collect owed protocol fees before burning the entirety of the liquidity position, preventing "position not found" panics.
   All 6 core tests now pass properly in debug/release profiles:
   test_tick_out_of_bounds
   test_invalid_tick_range
   test_concentrated_liquidity_swap
   test_concentrated_liquidity_mint
   test_burn_and_collect
   test_dynamic_fee_scaling
   Validation Results
   Running cargo test -p swap now yields a 100% pass rate.

shell
running 6 tests
test tests::test_tick_out_of_bounds - should panic ... ok
test tests::test_invalid_tick_range - should panic ... ok
test tests::test_concentrated_liquidity_swap ... ok
test tests::test_concentrated_liquidity_mint ... ok
test tests::test_burn_and_collect ... ok
test tests::test_dynamic_fee_scaling ... ok
test result: ok. 6 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.47s

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[RemmyAcee]

Done, Close: #307