feat(server): initialize project skeleton with db and api setup

Establish the foundational structure for the ez-api server.

Key changes include:
- Set up main entry point with graceful shutdown and Gin router
- Configure database connections for PostgreSQL (GORM) and Redis
- Define core data models (User, Provider, Key, Model)
- Implement configuration loading and basic key creation handler
- Add Dockerfile for multi-stage builds and .gitignore

cmd/server/main.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/ez-api/ez-api/internal/api"
+	"github.com/ez-api/ez-api/internal/config"
+	"github.com/ez-api/ez-api/internal/model"
+	"github.com/ez-api/ez-api/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/redis/go-redis/v9"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+)
+
+func main() {
+	// 1. Load Configuration
+	cfg, err := config.Load()
+	if err != nil {
+		log.Fatalf("Failed to load config: %v", err)
+	}
+
+	// 2. Initialize Redis Client
+	rdb := redis.NewClient(&redis.Options{
+		Addr:     cfg.Redis.Addr,
+		Password: cfg.Redis.Password,
+		DB:       cfg.Redis.DB,
+	})
+
+	// Verify Redis connection
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if err := rdb.Ping(ctx).Err(); err != nil {
+		log.Fatalf("Failed to connect to Redis: %v", err)
+	}
+	log.Println("Connected to Redis successfully")
+
+	// 3. Initialize GORM (PostgreSQL)
+	db, err := gorm.Open(postgres.Open(cfg.Postgres.DSN), &gorm.Config{})
+	if err != nil {
+		log.Fatalf("Failed to connect to PostgreSQL: %v", err)
+	}
+	sqlDB, err := db.DB()
+	if err != nil {
+		log.Fatalf("Failed to get generic database object: %v", err)
+	}
+	// Verify DB connection
+	if err := sqlDB.Ping(); err != nil {
+		log.Fatalf("Failed to ping PostgreSQL: %v", err)
+	}
+	log.Println("Connected to PostgreSQL successfully")
+
+	// Auto Migrate
+	if err := db.AutoMigrate(&model.User{}, &model.Provider{}, &model.Key{}, &model.Model{}); err != nil {
+		log.Fatalf("Failed to auto migrate: %v", err)
+	}
+
+	// 4. Setup Services and Handlers
+	syncService := service.NewSyncService(rdb)
+	handler := api.NewHandler(db, syncService)
+
+	// 5. Setup Gin Router
+	r := gin.Default()
+
+	// Health Check Endpoint
+	r.GET("/health", func(c *gin.Context) {
+		c.String(http.StatusOK, "OK")
+	})
+
+	// API Routes
+	r.POST("/keys", handler.CreateKey)
+
+	srv := &http.Server{
+		Addr:    ":" + cfg.Server.Port,
+		Handler: r,
+	}
+
+	// 6. Start Server with Graceful Shutdown
+	go func() {
+		log.Printf("Starting ez-api on port %s", cfg.Server.Port)
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("Server failed: %v", err)
+		}
+	}()
+
+	// Wait for interrupt signal
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
+	<-quit
+	log.Println("Shutting down server...")
+
+	// Shutdown with timeout
+	ctx, cancel = context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(ctx); err != nil {
+		log.Fatalf("Server forced to shutdown: %v", err)
+	}
+
+	log.Println("Server exited properly")
+}