Use POST /media for file upload

The old `/media/upload` subpath does not follow the convention of REST APIs.

Signed-off-by: David Mehren <git@herrmehren.de>

docs/dev/public_api.yml

@@ -454,7 +454,7 @@ paths:
           content:
             text/plain:
               example: my-note
-  /media/upload:
+  /media:
     post:
       tags:
         - media

src/api/public/media/media.controller.ts

@@ -23,7 +23,7 @@ export class MediaController {
     this.logger.setContext(MediaController.name);
   }
 
-  @Post('upload')
+  @Post()
   @UseInterceptors(FileInterceptor('file'))
   async uploadImage(
     @UploadedFile() file: MulterFile,