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/handler/health.go

@@ -0,0 +1,32 @@
+package handler
+
+import (
+	"net/http"
+	"time"
+
+	"gorm.io/gorm"
+	"github.com/gin-gonic/gin"
+)
+
+type HealthHandler struct {
+	db *gorm.DB
+}
+
+func NewHealthHandler(db *gorm.DB) *HealthHandler {
+	return &HealthHandler{db: db}
+}
+
+func (h *HealthHandler) Check(c *gin.Context) {
+	sqlDB, err := h.db.DB()
+	if err != nil {
+		c.String(http.StatusInternalServerError, "DB connection error: "+err.Error())
+		return
+	}
+
+	if err := sqlDB.Ping(); err != nil {
+		c.String(http.StatusInternalServerError, "DB unreachable: "+err.Error())
+		return
+	}
+
+	c.String(http.StatusOK, "Database connected. Server time: %s", time.Now().Format(time.RFC3339))
+}