refactor: Gitea 式目录改组，移除本分支 SPA 与杂项产物

将 model/service/handler/middleware 迁至 models/services/routers/api/modules/auth，并删除 frontend、embed_static、scripts 及误入库缓存/二进制。

Co-authored-by: Cursor <cursoragent@cursor.com>

services/upload.go

@@ -0,0 +1,18 @@
+package service
+
+import (
+	"mime/multipart"
+)
+
+var allowedImageExt = map[string]bool{
+	".jpg":  true,
+	".jpeg": true,
+	".png":  true,
+	".gif":  true,
+	".webp": true,
+}
+
+// SaveUploadedImage 保存图片到当前存储后端，返回公开 URL
+func SaveUploadedImage(store *UploadStore, file *multipart.FileHeader, category, namePrefix string) (string, error) {
+	return store.SaveImage(file, category, namePrefix)
+}