@spec delete_language(String.t(), String.t(), String.t(), integer() | nil) ::
  :ok | {:error, term()}

Deletes a specific language file from a post.

For versioned posts, specify the version. For legacy posts, version is ignored. Refuses to delete the last remaining language file.

Returns :ok on success or {:error, reason} on failure.

@spec delete_version(String.t(), String.t(), integer()) :: :ok | {:error, term()}

Deletes an entire version of a post.

Moves the version folder to trash instead of permanent deletion. Refuses to delete the last remaining version or the published version.

Returns :ok on success or {:error, reason} on failure.

@spec trash_language(String.t(), String.t()) :: {:ok, String.t()} | {:error, term()}

Moves a language file to trash (legacy operation, now just deletes).

@spec trash_post(String.t(), String.t()) :: {:ok, String.t()} | {:error, term()}

Moves a post to the trash folder.

For slug-mode groups, moves the entire post directory (all versions and languages). For timestamp-mode groups, moves the time folder.

The post directory is moved to: priv/publishing/trash/<group_slug>/<post_identifier>-<timestamp>/ (or priv/blogging/trash/... for legacy groups)

Returns {:ok, trash_path} on success or {:error, reason} on failure.