fix(x/precisebank): Ensure exact reserve balance on integer carry when minting

[drklee3]

Description

• Fix reserve minting an extra coin when the recipient module both carries fractional over to integer balance AND remainder is insufficient.
• Adjusts fractional carry to simply send from reserve, instead of doing an additional mint.
• Add invariant to ensure reserve matches exactly with fractional balances + remainder, failing on both insufficient and excess funds.