feat: add recipient param to PoolManager.burn

[BhariGowda]

Problem

PoolManager.burn() always credits the positive delta to msg.sender.
There is no way to direct the credit to a different address without a
multi-step workaround (burn → take → transfer), costing extra gas and
adding unnecessary complexity for router/hook integrators.

Fixes #985

Solution

Add a new 4-argument overload:

function burn(address from, address recipient, uint256 id, uint256 amount) external;

The positive delta is credited to recipient instead of msg.sender.
If recipient is address(0), it defaults to msg.sender for safety.

The existing 3-argument burn() is unchanged — fully backwards compatible.

Changes

• src/interfaces/IPoolManager.sol — new overload in interface
• src/PoolManager.sol — new overload implementation
• src/test/ProxyPoolManager.sol — new overload in proxy

Tests

603 tests pass. The 1 failure is a pre-existing TickMath edge case
unrelated to this change (present on main before any modifications).