feat: x/precisebank module

[dudong2]

Description

TL;DR: Introduces x/precisebank to address EVM ↔ SDK precision mismatch and integrates it with x/vm and precompiles.

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Problem

• Cosmos SDK assumes a 6-decimal denomination across all modules.
• EVM uses 18 decimals, causing precision loss when transferring values or paying gas.
• Sub-6-decimal values are floored, which can lead to:
  • Loss of small token amounts
  • Arbitrage vulnerabilities in DEXs like Uniswap v2 navite coin -> erc20 senarios due to mismatched balance handling

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Purpose

• Enable precise handling of fractional balances in EVM-related modules.
• Preserve and manage sub-integer values (e.g., 0.0000001 (= 10^-7) tokens) without loss.
• Seamlessly integrate precise value tracking into x/vm and precompiles.

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Implemented Changes

• Introduced a new x/precisebank module based on Kava’s implementation.
• Generalized to support 1~17 decimal assets, not just 6↔18.
• Added carry/borrow mechanics for converting fractional to integer coins.
• Replaced direct use of BankKeeper with PreciseBankKeeper in:
  • x/vm
  • precompiles
• Added invariant check for total supply
• Added CLI queries for fractional balances and remainder state.
• Added tests:
  • Edge case handling
  • Fuzz tests (Mint, Burn, Send, Genesis validation)

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Notes

• For tokens with exactly 18 decimals, use x/bank instead of x/precisebank.
• This module is designed to manage fractional precision below 6 decimals, not full 18-decimal coins.
• Staking, slashing, distribution, and other Cosmos SDK modules remain unchanged:
  • They all assume 6 decimals and are out of scope for this PR.

Closes: #48

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