refactor: enhance permission handling and introduce new Permission and Policy classes

- Updated the `Guard` class to improve permission checking by utilizing the new `Permission` class.
- Refactored tests in `authorize.spec.ts` to use `Permission` instances instead of strings for better type safety.
- Introduced a new `permissions.spec.ts` file to test the functionality of the `Permission` and `Policy` classes.
- Enhanced the `recursivelyReplacePlaceholders` utility function to support various object structures and types.
- Updated middleware and controller files to align with the new permission handling structure.

app/src/media/api/MediaController.ts

@@ -186,7 +186,8 @@ export class MediaController extends Controller {
             }),
          ),
          jsc("query", s.object({ overwrite: s.boolean().optional() })),
-         permission([DataPermissions.entityCreate, MediaPermissions.uploadFile]),
+         permission(DataPermissions.entityCreate),
+         permission(MediaPermissions.uploadFile),
          async (c) => {
             const { entity: entity_name, id: entity_id, field: field_name } = c.req.valid("param");