feat: implement auto-create linked notes on card add

[lPhiNix]

This PR adds an auto-create note feature to Kanban boards, allowing cards to automatically generate a linked Obsidian note upon creation, instead of holding plain text inline.

When the "Auto-create note on card add" toggle is enabled (disabled by default), clicking the "Add a card" button will:

1. Resolve a note name from a configurable template (default: {{board}}-{{id}})
2. Create a new Markdown note in the folder defined by the existing "Note folder" setting
3. Apply the existing "Note template" setting to the new note
4. Open the note in a split pane (same behavior as the native "New note from card" menu action)
5. Insert a wikilink to that note as the card content. e.g. [[MYBOARD-1]]
6. Persist the incremental counter inside the board's own settings block so it survives restarts and stays independent per board

Both the toggle and the format field are available at the global level and can be overridden per board, following the existing settings hierarchy.

All three card insertion modes (append, prepend, prepend-compact) are supported.

Why this is useful

The native workflow in Obsidian Kanban treats the card title as the source of truth, the text lives inside the board file itself. This works well for simple task tracking, but breaks down when you need the card and its content to be independent artifacts.

I hope you like these changes and I'll adjust anything you need!