Simplified project onboarding

### Describe the problem

Getting started with Weblate might be challenging in some situations because the import starts with creating a project and then components, while users typically want to start by providing the content to localize. The intention is to make this task-oriented (the user wants to translate these things) rather than model-oriented (to translate in Weblate you need to create projects and components).

### Solution brainstorm

I'd like to see more wizard-like imports in addition to the existing manual project/component creation. Perhaps it could be called “Import translatable content”.

1. Choose a workspace (or automatic selection if it is clear from the user).
2. Select an origin of the translations (code-hosting integration, VCS repository, import from other platforms).
3. Weblate scans the origin and proposes project and component configuration (including guided presets for component discovery).
4. The user is shown a preview with the option to change individual settings.
5. Everything is imported.

### Describe alternatives you have considered

_No response_

### Screenshots

_No response_

### Additional context

https://github.com/WeblateOrg/weblate/issues/20130 covers part of this.

No files, tests, or entry points are identified. Start by reviewing Weblate's existing manual project/component creation and import flows, then compare them with the related issue 20130; the work is done when the proposed content-first onboarding flow has an agreed design and implementation scope.

Written by the indexing model from the issue text.