refactor: remove mode from theme

[lukewalczak]

Changes

The main purpose of this PR is removing the concept of theme modes (adaptive and exact) that were previously used to control how dark theme was applied. This simplifies the theming system by removing this additional layer of complexity, making the dark theme behavior more straightforward and consistent.

1. Documentation Changes:

• Removed documentation about dark theme modes (adaptive and exact) from the theming guide
• Removed references to dark theme mode in component documentation

2. Theme Changes:

• Removed mode: 'adaptive' from theme
• Removed mode-related theme overrides from example components

3. Card Component:

• Removed dark adaptive mode logic and animations
• Simplified elevation animation to use a single animated value

[github-actions[bot]]

The mobile version of example app from this branch is ready! You can see it here.

[callstack-bot]

Hey @lukewalczak, thank you for your pull request 🤗. The documentation from this branch can be viewed here.