chore: android technical housekeeping

[ovitrif]

Goal

Bring Bitkit Android's engineering foundation to a current, internally consistent state through independently owned maintenance issues with measurable acceptance criteria and product-level verification.

GitHub sub-issues are the source of truth for child scope and completion. GitHub blocked-by relationships are the source of truth for ordering and start gates. Do not re-list children or dependency prose in this description.

The Kotlin/Compose child also specifies follow-up issues for version-specific AI rules and current-language-feature code style. The Navigation 3 child owns an ordered series of separate-concern pull requests.

Acceptance criteria

• Each pull request is reviewed, approved, validated, and merged independently.
• Navigation 3 lands through the ordered incremental series with a runnable, tested app after every merge.
• Final master passes the combined build, test, lint, device, E2E, journey, release, and documentation checks applicable to the changed surfaces.
• The Bitkit project item reaches ✅ Done after acceptance, review, check, and merge gates complete.