Phase 0: project scaffold

- Go module + chi server with embedded SPA serving and /api/health
- internal/config env loader (local-dev defaults; auth/copyleaks deferred)
- React 19 + Vite 6 + Tailwind v4 frontend with full Petal design tokens
- Frontend embedded into the binary via web/embed.go (go:embed all:dist)
- README dev workflow, .env.example, BUILD_PLAN progress tracker
- Verified end-to-end: binary serves health, embedded SPA, and SPA fallback

.gitignore

@@ -0,0 +1,23 @@
+# Go
+/petal
+*.exe
+*.test
+*.out
+
+# Node / frontend
+web/node_modules/
+web/dist/*
+!web/dist/.gitkeep
+*.log
+
+# Local env & data
+.env
+*.db
+*.db-shm
+*.db-wal
+/data/
+
+# Editor / OS
+.DS_Store
+.vscode/
+.idea/