Phase 0: backend + frontend scaffold, single-binary build

Implements the Pansy v1 scaffold (epic #20, phase 0).

#1 Backend: Go module (pure-Go, builds with CGO_ENABLED=0), env config,
   gin server with slog + recovery + /api/v1/healthz, modernc SQLite store
   with WAL/busy_timeout/foreign_keys pragmas, embedded numbered-migration
   runner, full initial schema (users, sessions, gardens, garden_shares,
   garden_objects, plants, plantings), domain structs + sentinel errors,
   graceful shutdown.

#2 Frontend: Vite + React 19 + TS (strict) + Tailwind 4 + TanStack
   Router/Query, typed /api/v1 fetch wrapper (ApiError carries status +
   body so later issues can read 409 conflict rows), dev proxy /api -> :8080,
   responsive app shell with stub pages for all five routes.

#3 Single binary: //go:embed of the web build with a committed placeholder,
   SPA fallback (deep links, immutable asset caching, JSON 404 for unmatched
   /api and missing assets), Makefile (web/build/dev/test), README quickstart
   + env var table.

Verified: go build/vet/test clean (CGO off); binary migrates idempotently and
serves healthz; web tsc + build clean; integrated binary serves the SPA, deep
links, and correct cache headers; app mounts and navigates all five routes at
desktop and 375px widths.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

cmd/pansy/main.go

@@ -0,0 +1,87 @@
+// Command pansy is the single static binary: it loads configuration, opens and
+// migrates the SQLite database, builds the HTTP server (JSON API + embedded SPA),
+// and serves until interrupted.
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/api"
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/config"
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/store"
+	"gitea.stevedudenhoeffer.com/steve/pansy/internal/webdist"
+)
+
+func main() {
+	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelInfo})))
+
+	if err := run(); err != nil {
+		slog.Error("pansy: fatal", "error", err)
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	cfg := config.Load()
+
+	db, err := store.Open(cfg.DBPath)
+	if err != nil {
+		return fmt.Errorf("open database: %w", err)
+	}
+	defer db.Close()
+
+	// Migrations run against a short-lived context so a hung DB can't block boot
+	// forever; the schema is tiny so this is generous.
+	migCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	if err := db.Migrate(migCtx); err != nil {
+		return fmt.Errorf("migrate database: %w", err)
+	}
+	slog.Info("pansy: database ready", "path", cfg.DBPath)
+
+	r := api.New(cfg)
+	api.RegisterSPA(r, webdist.Dist())
+
+	srv := &http.Server{
+		Addr:              fmt.Sprintf(":%d", cfg.Port),
+		Handler:           r,
+		ReadTimeout:       15 * time.Second,
+		ReadHeaderTimeout: 5 * time.Second,
+		WriteTimeout:      30 * time.Second,
+		IdleTimeout:       60 * time.Second,
+	}
+
+	// Serve in the background; the main goroutine waits for a signal, then drains.
+	serveErr := make(chan error, 1)
+	go func() {
+		slog.Info("pansy: listening", "addr", srv.Addr)
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			serveErr <- err
+		}
+	}()
+
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+
+	select {
+	case err := <-serveErr:
+		return fmt.Errorf("http server: %w", err)
+	case <-ctx.Done():
+		slog.Info("pansy: shutting down")
+		stop() // restore default signal handling so a second Ctrl-C force-quits
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+		defer cancel()
+		if err := srv.Shutdown(shutdownCtx); err != nil {
+			return fmt.Errorf("graceful shutdown: %w", err)
+		}
+	}
+	return nil
+}