## Price Calculation Fix
- Fix inconsistent price calculation between BUY and SELL operations
- Ensure both sides return price in same units (quote per base token)
- BUY operations now return comparable prices to SELL operations

## Decimal Handling Fix
- Replace flawed toFixed() approach with ethers parseUnits()
- Prevent "fractional component exceeds decimals" errors
- Handle all token decimals correctly (6 for USDC, 18 for ETH, etc.)

## EIP-1559 Gas Pricing
- Implement proper EIP-1559 gas pricing for supported networks
- Calculate maxFeePerGas as 2 * baseFee + maxPriorityFeePerGas
- Graceful fallback to legacy pricing when needed
- Fix "max fee per gas less than block base fee" errors

## Approval System Improvements
- Add @fastify/sensible plugin for proper error handling
- Implement intelligent allowance checking for Permit2 flow
- Skip unnecessary approval transactions when allowances exist
- Increase timeout from 12s to 60s for approval transactions
- Add null checks for transaction receipts

## Performance & UX Enhancements
- Skip ERC20 approval if sufficient allowance exists
- Skip Permit2 approval if sufficient unexpired allowance exists
- Instant response when no approvals needed
- Significant gas savings for repeat users

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

fix: comprehensive Uniswap router and approval improvements