chore(architecture): add anki-common module skeleton

[david-allison]

Note

Assisted-by: Claude Opus 4.7 - almost all

Purpose / Description

This is designed for common files which also depend on libanki, therefore cannot be inside common or common:android.

Initially, this is to implement the Destination concern: navigation between Activities needs DeckId (can't be in :common), and wouldn't be able to have circular dependencies, so couldn't live in feature modules when we move to them

Fixes

• Related Abstract browser access with BrowserDestinations #20558
• Related Architecture Discussion: Module Extraction #20737
• Split from arch: introduce 'Destination' pattern #21023

Approach

See README.md

For example, CollectionManager should live here:

• Not in libanki
• libanki dependency
• Common code

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner