fix: serve doc.json via swag.ReadDoc in SwaggerHandler

The custom SwaggerHandler was missing doc.json, causing Swagger UI
to fail loading the API specification.

internal/app/middleware/swagger.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	swaggerFiles "github.com/swaggo/files"
+	"github.com/swaggo/swag"
 	"github.com/gin-gonic/gin"
 )
 
@@ -24,6 +25,16 @@ func SwaggerHandler() gin.HandlerFunc {
 
 		isCSS := strings.HasSuffix(relPath, "swagger-ui.css")
 		isInitializer := strings.HasSuffix(relPath, "swagger-initializer.js")
+		isDocJSON := strings.HasSuffix(relPath, "doc.json")
+
+		if isDocJSON {
+			doc := swag.ReadDoc()
+			c.Header("Content-Type", "application/json; charset=utf-8")
+			c.Writer.WriteHeader(200)
+			c.Writer.Write([]byte(doc))
+			c.Request.URL.Path = rawPath
+			return
+		}
 
 		if isInitializer {
 			c.Header("Content-Type", "application/javascript; charset=utf-8")