[Claim Settlement] Replace float tokenomics calculations by big.Rat

[red-0ne]

Objective

Ensure predictable and precision-loss-free claim settlement rewards.

Origin Document

Pending claims settlement rewards currently use floating-point calculations, which are imprecise and non-deterministic across different platforms.

Goals

• Achieve lossless and predictable reward calculations.

Deliverables

• A single PR replacing float types with big.Rat for pending claim settlement reward calculations.

Non-goals / Non-deliverables

• Implementing fixed-point arithmetic.
• Rewriting the pending claims settlement logic.

General deliverables

• Testing: Add new tests (unit and/or E2E) to the test suite.

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Creator: @red-0ne
Co-Owners: @Olshansk

[Olshansk]

@red-0ne This is going to be a fun one :)