feat: init sproutclaw-web — Go+Gin backend + React frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/static/static.go

@@ -0,0 +1,68 @@
+package static
+
+import (
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// Register attaches the static file handler to the Gin router.
+// distDir is the path to frontend/dist/.
+func Register(r *gin.Engine, distDir string) {
+	r.NoRoute(func(c *gin.Context) {
+		path := c.Request.URL.Path
+
+		// Skip API routes – they're handled elsewhere
+		if strings.HasPrefix(path, "/api/") {
+			c.JSON(http.StatusNotFound, gin.H{"error": "not found"})
+			return
+		}
+
+		// Try to serve a real file
+		fsPath := filepath.Join(distDir, filepath.FromSlash(path))
+		if info, err := os.Stat(fsPath); err == nil && !info.IsDir() {
+			serveFile(c, fsPath)
+			return
+		}
+
+		// SPA fallback: serve index.html
+		indexPath := filepath.Join(distDir, "index.html")
+		if _, err := os.Stat(indexPath); err != nil {
+			c.String(http.StatusNotFound, "frontend not built – run npm run build:web in frontend/")
+			return
+		}
+		c.Header("Cache-Control", "no-cache, no-store, must-revalidate")
+		c.File(indexPath)
+	})
+}
+
+func serveFile(c *gin.Context, fsPath string) {
+	name := filepath.Base(fsPath)
+	ext := strings.ToLower(filepath.Ext(name))
+
+	if name == "index.html" || strings.HasSuffix(name, ".webmanifest") {
+		c.Header("Cache-Control", "no-cache, no-store, must-revalidate")
+	} else if isHashedAsset(name, ext) {
+		c.Header("Cache-Control", "public, max-age=31536000, immutable")
+	} else if ext == ".woff" || ext == ".woff2" || ext == ".ttf" || ext == ".otf" {
+		c.Header("Cache-Control", "public, max-age=31536000, immutable")
+	} else {
+		c.Header("Cache-Control", "public, max-age=3600")
+	}
+
+	// Gin's File() handles Content-Type and ETag automatically
+	c.File(fsPath)
+}
+
+// isHashedAsset returns true if the filename looks like a Vite hashed asset
+// (e.g. index-BxYt3k2a.js, chunk-abc123.css).
+func isHashedAsset(name, ext string) bool {
+	switch ext {
+	case ".js", ".css", ".mjs":
+		return strings.Contains(name, "-") || strings.Contains(name, ".")
+	}
+	return false
+}