Phase 6: Uniswap V4 Support

## Phase 6: Uniswap V4 Support

Parent Issue: #98

### Overview
Implement Uniswap V4 integration to leverage the latest protocol features for better gas efficiency and advanced swap capabilities.

### Tasks

#### V4 Integration
- [ ] Integrate Uniswap V4 SDK
- [ ] Implement V4 pool detection and routing
- [ ] Add support for singleton contract architecture
- [ ] Optimize gas efficiency with V4's flash accounting
- [ ] Handle V4-specific quote fetching

#### Custom Hooks Support
- [ ] Implement support for V4 custom hooks
- [ ] Add hook detection and validation
- [ ] Support dynamic fees from hooks
- [ ] Handle hook-specific swap parameters
- [ ] Add UI indicators for pools with custom hooks

#### Multi-Hop Swaps
- [ ] Implement multi-hop routing algorithm
- [ ] Add support for complex swap paths (A → B → C)
- [ ] Optimize route finding for best rates
- [ ] Display multi-hop routes in UI
- [ ] Show intermediate tokens in swap preview
- [ ] Calculate and display total slippage across hops

#### Testing
- [ ] Test V4 swaps on testnet
- [ ] Test custom hooks integration
- [ ] Test multi-hop routing
- [ ] Verify gas savings vs V3
- [ ] Test edge cases (low liquidity, high slippage)

#### Documentation
- [ ] Document V4 integration architecture
- [ ] Add developer guide for V4 features
- [ ] Document custom hooks support
- [ ] Add multi-hop routing documentation

### Technical Notes

**Uniswap V4 Key Features:**
- Singleton contract design (all pools in one contract)
- Flash accounting for gas optimization
- Custom hooks for extensibility
- Native ETH support
- Improved capital efficiency

**Multi-Hop Routing:**
- Should find optimal path across V3 and V4 pools
- Consider gas costs in route optimization
- Support up to 3-4 hops maximum
- Fallback to direct swap if multi-hop has worse rate

**Custom Hooks Considerations:**
- Hooks can modify swap behavior (fees, limits, etc.)
- Need to validate hook safety before executing
- Display hook information to users for transparency
- Some hooks may require additional approvals

### Dependencies
- Requires Phase 1-5 completion
- Uniswap V4 SDK (when available on mainnet)
- Updated router contracts

### Success Criteria
- [ ] V4 swaps execute successfully with lower gas costs
- [ ] Custom hooks are properly detected and handled
- [ ] Multi-hop routing finds better rates than single-hop
- [ ] UI clearly shows V4 features and multi-hop paths
- [ ] All tests pass

### Related Issues
- Parent: #98 (Token Swap Integration)
- Depends on: Phase 1-5 completion