Contract: add MIN_DEPOSIT (500e6) + BelowMinimum error, checked against the
combined credit (stable leg + valued stock leg) in _deposit, so it covers
single- and dual-sided deposits. Tests updated (sub-$500 fixtures raised,
fuzz bounds lifted) plus three new cases; 33/33 pass. ABI regenerated.
Frontend: pre-submit validation in AppBoard and DepositPanel — button
disables with a "Min. deposit $500" label and an inline error below the
minimum, so users get feedback before signing. Shared MIN_DEPOSIT_USD /
MIN_DEPOSIT_UNITS constants. Also refreshes the local anvil addresses in the
dev deployment block (dev-only; prod uses the seed).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>