Upgrade Global Search to look inside files content and metadata

### Background

The current implementation of the **Global Search** feature has some minor limitations for searching in object storages - files can be founded only by their names.
It would be convenient to extend the **Global Search** feature so that users can also search files through:
- file contents
- file metadata (tags)

The issue describes the Global Search feature and object storage, but names no implementation files, tests, or entry points. Start by locating the Global Search implementation and its existing filename search behavior, then determine how file contents and metadata tags should be indexed and queried; done means both are searchable alongside filenames.

Written by the indexing model from the issue text.