refactor: extract activity animationEnabled/animationDisabled into :common:android

[david-allison]

Note

Assisted-by: Claude Opus 4.8 - all

Purpose / Description

Note: this is also an initial pattern for Profile-aware Preferences in a multimodule situation

Note: This also sets a pattern for handling singletons in EmptyApplication

AnkiActivity needs to be moved to common as prep for multi-modules: it needs to be below feature modules which use it.

I'm focusing on AnkiActivity due to :widgets containing:

class CardAnalysisWidgetConfig : AnkiActivity(R.layout.activity_card_analysis_widget_config)

This PR extracts 'animations' from AnkiActivity: moving them to extension methods on FragmentActivity.

Fixes

• Part of Architecture Discussion: Module Extraction #20737

Approach

See commits: iterative extractions

How Has This Been Tested?

⚠️ Untested, should be typical refactors.

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