Initial fullstack project setup with Next.js 15, Gin, PostgreSQL and Docker Compose

- Frontend: Next.js 15 (App Router), Auth.js v5, shadcn/ui, MagicUI
- Backend: Go + Gin + GORM with layered architecture
- Auth: Local credentials login with optional Keycloak OAuth binding
- Admin: RBAC user management for admin role
- Dev: Docker Compose with hot reload for both frontend and backend
- Docker: 3-service orchestration (frontend, backend, postgres)

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

backend/internal/middleware/auth.go

@@ -0,0 +1,23 @@
+package middleware
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+func AuthProxy() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		userID := c.GetHeader("X-User-Id")
+		userRole := c.GetHeader("X-User-Role")
+
+		if userID == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "unauthorized"})
+			return
+		}
+
+		c.Set("userID", userID)
+		c.Set("userRole", userRole)
+		c.Next()
+	}
+}