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

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

Fix zigzag zone boundaries: correct strip generation coordinate math

Improve crop-aware zone generation: generate rectangular strips per-crop instead of post-hoc clipping

Implement Changes 4.2 and 5.1-5.2: Multi-source water support and crop-aware zone refinement

Change 2: Implement strip-based rectangular zone splitting

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

fix: add area-density floor to valve placement (5 valves/ha generic)

feat: multi-unit input/display support + valve engine corrections

Phase 1.5: valve placement engine with hierarchical decision matrix