Update Gradio sdk_version to 6.14.0 to fix static asset 404s

Add REST /api/v1/design endpoint accepting farm/plots/water_sources

Revert to working Gradio 6.13.0 config (commit e707387 was RUNNING)

Fix: use Gradio 5.4.0 (stable, works on HF Spaces)

Fix HF Space: downgrade Gradio to stable version 4.44.1

Phase 1: geometry engine + Gradio UI for drip irrigation design

initial commit