feat: implement single binary build and env-based auth

- Unify login page styling with share page
- Add AGENTS.md with build commands and code style guidelines
- Add dev.sh and make.sh for development and production builds
- Implement single binary build with embedded frontend using embed.FS
- Change auth configuration from CLI flag to env variables (USHARE_USERNAME, USHARE_PASSWORD)
- Set default credentials: admin / ushare@123
- Fix static file serving for SPA routes

internal/handler/static.go

@@ -0,0 +1,114 @@
+package handler
+
+import (
+	"github.com/loveuer/nf"
+	"github.com/loveuer/nf/nft/log"
+	"github.com/loveuer/ushare/internal/static"
+	"io"
+	"io/fs"
+	"net/http"
+	"strings"
+)
+
+func ServeFrontend() nf.HandlerFunc {
+	assets := static.Frontend()
+
+	return func(c *nf.Ctx) error {
+		path := strings.TrimPrefix(c.Path(), "/")
+		if path == "" || path == "/" {
+			path = "index.html"
+		}
+
+		file, err := assets.Open(path)
+		if err != nil {
+			if err.Error() == "file does not exist" {
+				return serveIndex(assets, c)
+			}
+			return c.SendStatus(http.StatusNotFound)
+		}
+		defer file.Close()
+
+		stat, err := file.Stat()
+		if err != nil {
+			return c.SendStatus(http.StatusInternalServerError)
+		}
+
+		if stat.IsDir() {
+			return serveIndex(assets, c)
+		}
+
+		io.Copy(c.Writer, file)
+		return nil
+	}
+}
+
+func ServeFrontendMiddleware() nf.HandlerFunc {
+	assets := static.Frontend()
+
+	return func(c *nf.Ctx) error {
+		path := c.Path()
+
+		if strings.HasPrefix(path, "/api") || strings.HasPrefix(path, "/ushare") {
+			return c.Next()
+		}
+
+		filePath := strings.TrimPrefix(path, "/")
+		if filePath == "" || filePath == "/" {
+			filePath = "index.html"
+		}
+
+		file, err := assets.Open(filePath)
+		if err != nil {
+			return serveIndex(assets, c)
+		}
+		defer file.Close()
+
+		stat, err := file.Stat()
+		if err != nil {
+			return c.SendStatus(http.StatusInternalServerError)
+		}
+
+		if stat.IsDir() {
+			return serveIndex(assets, c)
+		}
+
+		c.SetHeader("Content-Type", getContentType(filePath))
+		io.Copy(c.Writer, file)
+		return nil
+	}
+}
+
+func serveIndex(assets fs.FS, c *nf.Ctx) error {
+	index, err := assets.Open("index.html")
+	if err != nil {
+		log.Error("failed to open index.html: %v", err)
+		return c.SendStatus(http.StatusInternalServerError)
+	}
+	defer index.Close()
+
+	c.SetHeader("Content-Type", "text/html; charset=utf-8")
+	io.Copy(c.Writer, index)
+	return nil
+}
+
+func getContentType(path string) string {
+	if strings.HasSuffix(path, ".html") {
+		return "text/html; charset=utf-8"
+	}
+	if strings.HasSuffix(path, ".css") {
+		return "text/css; charset=utf-8"
+	}
+	if strings.HasSuffix(path, ".js") {
+		return "application/javascript; charset=utf-8"
+	}
+	if strings.HasSuffix(path, ".png") {
+		return "image/png"
+	}
+	if strings.HasSuffix(path, ".jpg") || strings.HasSuffix(path, ".jpeg") {
+		return "image/jpeg"
+	}
+	if strings.HasSuffix(path, ".svg") {
+		return "image/svg+xml"
+	}
+	return "application/octet-stream"
+}