feat: Compose setup for project

[criticalAY]

Purpose / Description

Enable Jetpack Compose on the :AnkiDroid module so future screens can be built or migrated incrementally. This follows Google's I/O 2026 "Compose-First" direction. This PR is foundational it does not convert any existing user-facing screen.

Fixes

• Related to Incremental Jetpack Compose adoption #21138

Approach

See commit 1 and then:
Added com.ichi2.compose.theme.Theme that reads colors from the host Activity's XML theme via R.styleable.ComposeTheme and bridges each of the four AnkiDroid themes (Light, Plain, Dark, Black) into a Material 3 ColorScheme. Slots not declared by the XML fall back to Material 3 defaults; isLightTheme (inherited from Theme.Material3.{Light,Dark}) decides the base scheme.

• Add ktlint config: ktlint_function_naming_ignore_when_annotated_with = Composable so @composable fun MySomeScreen() isn't flagged.

How Has This Been Tested?

Local build passed

Learning (optional, can help others)

Themes and Preview is a mess to handle for custom themes and it took me whole night to enable compose for Shared Deck screen

Checklist

Please, go through these checks before submitting the PR.

• 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

[david-allison]

LooksGreatToMe!!