Switch MainActivity to XML layout and add HomeScreen UI + components

[ZBZFirst]

Motivation

• Prepare a simple hybrid UI by switching the activity to an XML-based palette canvas while introducing a Compose-based home screen and reusable UI components.
• Scaffold future features and navigation by adding placeholders for camera/export pipelines and a navigation object.

Description

• Replace Compose setContent in MainActivity with setContentView(R.layout.activity_main) and remove the example Greeting composable and previews.
• Add an XML layout res/layout/activity_main.xml and new string resources in res/values/strings.xml to provide a palette-style canvas view for the activity.
• Add a Compose app entry TempleIApp, a HomeScreen with state (HomeUiState, HomeEvent), and UI components PulseButton and UiPaletteBar with previews to drive the in-app palette experience.
• Add lightweight placeholders for navigation (NavGraph, Routes) and features (CameraFeature, ExportFeature) and mark the Gradle wrapper gradlew as executable.

Testing

• No automated tests were run as part of this change.

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Codex Task