fix: make receive actions usable on compact screens

[Arbeitszeit]

Issue Number (if Applicable): N/A

Description

This change keeps the receive-page actions usable on compact Android screens and avoids displaying unavailable address metadata as literal null values.

Changes

• Use equal-width flexible action cells in the receive-page bottom row.
• Reduce button size, padding, and spacing below 400 logical pixels.
• Allow ModernButton labels to use up to two centered lines with ellipsis.
• Render transaction count and balance independently only when each value is available.
• Add widget coverage for Spanish labels at 320 px and 360 px widths.
• Add widget coverage for address rows whose metadata is unavailable.

Validation

• git diff --check passes.
• Widget tests were added, but could not be executed locally because the generated root pubspec and Flutter toolchain are not available in the analysis environment. CI validation is requested.

Pull Request - Checklist

• Initial Manual Tests Passed
• Double check modified code and verify it with the feature/task requirements
• Format code
• Look for code duplication
• Clear naming for variables and methods
• Manual tests in accessibility mode (TalkBack on Android) passed