Create a foundational Jetpack Compose theme to replace the temporary MDC3Theme adapter. This will standardize colors, typography, and shapes across the application.

• Create a Color.kt file with the app's color palette.

• Create a Type.kt file defining the typography scale (h1, body1, etc.).

• Create a Theme.kt file that combines colors and typography into a reusable theme.

• Apply the new base theme to the root composable.

• Remove the MDC3Theme adapter.