[L-3] FIXEDFEE Should Be constant Instead of immutable

Description

LikeRegistry declares:

FIXEDFEE is assigned at declaration time and never receives constructor input. In this pattern, constant is a more appropriate qualifier because the value is compile-time fixed.

Using constant makes intent clearer and can improve bytecode/runtime efficiency compared with a non-constructor immutable literal.

Risk

Likelihood: High

The declaration pattern is present in the current implementation.

Impact: Low

No direct security issue is introduced; this is a code-quality and gas-optimization finding.

Proof of Concept

Relevant lines:

• declaration: uint256 immutable FIXEDFEE = 10;

• usage: uint256 matchingFees = (totalRewards * FIXEDFEE) / 100;

There is no constructor parameter or runtime update path for FIXEDFEE.

Recommended Mitigation

Change FIXEDFEE to constant:

Optionally expose it as public constant if external visibility is needed for integrations or frontends.