Add app shell, HomeScreen, PulseButton and UI components with feature placeholders

[ZBZFirst]

Motivation

• Establish an application shell and central composable entrypoint to replace the previous inline Greeting scaffolding in MainActivity.
• Provide a simple interactive home screen and reusable UI components to iterate on the app's UI palette and pulse action.
• Add lightweight placeholders for navigation and domain features to reserve package structure for future work.

Description

• Replace the inline UI in MainActivity with a new top-level TempleIApp composable and remove the old Greeting and previews.
• Add TempleIApp which hosts a Scaffold and displays the new HomeScreen composable from ui.screens.home.
• Implement HomeScreen, HomeUiState, and HomeEvent to manage a small local UI state (selected palette item and flashing status) and handle a PulsePressed event.
• Add two reusable components: PulseButton (animated pulsing button with color animation) and UiPaletteBar (horizontally scrollable assist-chip palette), plus previews for both components.
• Add small placeholder objects for NavGraph, Routes, CameraFeature, and ExportFeature to reserve packages for navigation and feature pipelines.
• Make the Gradle wrapper executable (mode change on gradlew).

Testing

• Ran ./gradlew build to compile the app sources and resources, and the build completed successfully.
• Verified that Compose previews compile for PulseButton and HomeScreen as part of the build.

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Codex Task