Support configurable working directory and fuzzy repo selection

[GarrickZ2]

It would be very helpful to add support for a configurable Working Directory in Vibe Kanban.

1. Global / default Working Directory

Allow users to configure a default Working Directory in the settings.

When creating a new repository or browsing existing repositories, Vibe Kanban would use this Working Directory as the initial search root.

This would avoid having to manually change the “Search Folder” every time a user clicks Create New Repository or Browse Repository, especially for users who keep all their projects under a common parent directory (e.g. ~/Code, ~/workspace, etc.).

2. Fuzzy-search repo selection with fzf-style UX

When the user wants to select a repository path, allow typing a path prefix and then use a fuzzy-finder (e.g. fzf-like behavior) to quickly search for git repositories under the configured Working Directory.

Support recursive search with a configurable max depth so users can control how deep the tool looks for .git directories.

Present the matched repositories in an interactive list so the user can quickly filter and choose one, instead of manually navigating folders every time.

These two improvements would make repo selection much faster and smoother for users who work with many local git repositories under a common root.