Fix: Use StaticFS for assets to serve correct MIME types

backend/internal/api/routes/routes.go

@@ -1,6 +1,8 @@
 package routes
 
 import (
+	"net/http"
+
 	"sale/internal/api/handlers"
 	"sale/internal/api/middlewares"
 	"sale/internal/models"
@@ -206,20 +208,21 @@ func SetupRoutes(r *gin.Engine) {
 	// Serve uploads
 	r.Static("/uploads", "./uploads")
 
+	// Serve frontend static assets (CSS, JS, images, etc.)
+	r.StaticFS("/assets", http.Dir("./static/assets"))
+
 	// SPA fallback - serve index.html for all other routes (Vue Router History Mode)
 	// This must be the last route to catch all unmatched paths
 	r.NoRoute(func(c *gin.Context) {
 		path := c.Request.URL.Path
-		// Serve index.html for all non-API routes (Vue Router History Mode)
-		// But skip API, assets, and uploads paths
+		// For root and SPA routes, serve index.html
+		// API requests will return 404 if not found
 		if path == "/" || path == "/favicon.ico" || path == "/icons.svg" || path == "/favicon.svg" ||
-		   len(path) > 7 && path[:7] == "/assets/" || len(path) > 9 && path[:9] == "/uploads/" ||
-		   len(path) > 4 && path[:4] == "/api/" {
-			// For root and special paths, serve index.html directly
+		   len(path) > 4 && path[:4] != "/api/" {
 			c.File("/app/static/index.html")
 		} else {
-			// For all other routes, serve index.html (Vue Router handles client-side routing)
-			c.File("/app/static/index.html")
+			// API routes - let them return 404 if not found
+			c.AbortWithStatus(404)
 		}
 	})
 }