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

internal/api/handler.go

@@ -0,0 +1,42 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/ez-api/ez-api/internal/model"
+	"github.com/ez-api/ez-api/internal/service"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+type Handler struct {
+	db   *gorm.DB
+	sync *service.SyncService
+}
+
+func NewHandler(db *gorm.DB, sync *service.SyncService) *Handler {
+	return &Handler{db: db, sync: sync}
+}
+
+func (h *Handler) CreateKey(c *gin.Context) {
+	var key model.Key
+	if err := c.ShouldBindJSON(&key); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+
+	// Save to DB
+	if err := h.db.Create(&key).Error; err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create key", "details": err.Error()})
+		return
+	}
+
+	// Sync to Redis
+	if err := h.sync.SyncKey(&key); err != nil {
+		// Note: In a real system, we might want to rollback DB or retry async
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to sync key to Redis", "details": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusCreated, key)
+}