feat(api): Add Swagger UI for v1 endpoints

Serve interactive docs at /api, covering only the current /api/v1/*
endpoints. Deprecated /api/diyanet/* endpoints are left undocumented.

internal/api/api.go

@@ -261,6 +261,16 @@ func New(services Services) *fiber.App {
 		return ctx.JSON(mapped)
 	})
 
+	app.Get("/api/openapi.yaml", func(ctx fiber.Ctx) error {
+		ctx.Response().Header.Set(fiber.HeaderContentType, "application/yaml")
+		return ctx.Send(openapiSpec)
+	})
+
+	app.Get("/api", func(ctx fiber.Ctx) error {
+		ctx.Response().Header.Set(fiber.HeaderContentType, fiber.MIMETextHTMLCharsetUTF8)
+		return ctx.SendString(swaggerHTML)
+	})
+
 	app.Use("/", static.New("", static.Config{FS: templates.FS()}))
 
 	return app