hotfix: numpad layout to use weights and dynamic screen height

[isaacsa51]

Description

Changes made to fix the Numpad layout when editing an existing expense.

Change strategy

Refactored the Numpad component to use a weight-based internal layout instead of fixed row heights, allowing it to scale dynamically to a parent-defined percentage of the screen.

Implemented

• Refactored Numpad.kt to use Modifier.weight for rows.
• Updated TransactionEditScreen.kt to calculate and assign exactly 48% of screen height to the numpad.
• Added safety logic to ensure layout weights are always strictly positive to prevent IllegalArgumentException during transitions.

Working demo

Screen_recording_20260611_215709.webm

Testing

• Ran ./gradlew :app:compileDebugKotlin :wear:compileDebugKotlin :sync-contract:compileKotlin :app:testDebugUnitTest
• Added/updated tests when applicable
• Added screenshots or screen recordings for UI changes

Notes

N/A