feat: Initial OPHION structure

- Go backend with Fiber framework
- Agent for metrics collection
- Docker Compose for self-hosted
- Auth middleware (JWT + API Keys)
- Rate limiting
- Install script

internal/api/ratelimit.go

@@ -0,0 +1,27 @@
+package api
+
+import (
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/limiter"
+)
+
+func RateLimitMiddleware() fiber.Handler {
+	return limiter.New(limiter.Config{
+		Max:        100,              // 100 requests
+		Expiration: 1 * time.Minute,  // per minute
+		KeyGenerator: func(c *fiber.Ctx) string {
+			// Use API key or IP for rate limiting
+			if key := c.Locals("api_key"); key != nil {
+				return key.(string)
+			}
+			return c.IP()
+		},
+		LimitReached: func(c *fiber.Ctx) error {
+			return c.Status(429).JSON(fiber.Map{
+				"error": "Rate limit exceeded",
+			})
+		},
+	})
+}