Phase 5: Drip Manifold Alignment - valve-proximity manifold selection

Multi-pump optimization: Voronoi service partitioning and scoped valve placement

Fix lateral parallelism and uniformity: use farm-level direction for consistent lateral angles

Change 1: Implement global lateral orientation with compute_farm_axis

Improve design_api accuracy: crop propagation, valve distribution, smart centralized default, BOM pricing, UTM caching