fix: resolve issues 196, 197, 198

[a1denvalu3]

Summary

This PR addresses three distinct UI and logic issues:

• Fixes Button Text Doesnt Change on Theme Change #196: Replaced hardcoded @android:color/white on dialog buttons with theme-aware @color/color_bg_white so they invert correctly when the background switches to white in dark mode. Also fixed the background on the item variation add button to invert properly.
• Fixes Text Cutoff on "Add Item" Screen #197: Fixed text truncation on the "Add Item" screen by modifying the fixed 100dp layout widths on form labels to wrap_content with a minWidth. This ensures longer localized strings and different font scales don't get arbitrarily cut off.
• Fixes Incorrect Error and Disallowance of Price #198: Updated PricingHandler regex to allow user prices to start with a decimal separator (e.g. .55).