UI Improvements: PIN screen redesign, welcome screen updates, and gradient overlays

[stackedPenguin]

Changes

• Redesigned PIN unlock screen with background image, gradient overlay, and logo with blur effect
• Redesigned PIN setup screen to match the login PIN screen design
• Updated welcome screen with gradient overlays and blur logo effect
• Fixed keypad layout to standard 3 buttons per row
• Added safe area insets for proper padding on all PIN screens
• Improved spacing and centering of elements on PIN screens
• Updated create wallet flow to properly show seed phrase modal

Screens Updated

• PIN Setup screen
• PIN Unlock screen
• Welcome/Empty State screen

All changes maintain compatibility with existing master branch features (QR scanner, network switches, etc.).