HIGH: Theme Unification - Resolve visual discord between Corporate Blue and Cyberpunk Card Deck

[nathanbangwa243]

Issue

The application declares a "Corporate Clean Blue" theme but the Card Deck mode uses explicit cyberpunk neon styling (dark purples/blues, cyan, magenta). This creates visual discord across game modes.

Current State

• Corporate Clean Blue (Bingo, Scavenger Hunt): Blues (#0b61d1), whites, clean UI
• Cyberpunk (Card Deck): Dark gradients (#09001a, #2b0036), neon accents (#00e5ff, #ff00a8), text-shadow glows

Impact

• Users experience jarring visual transition when switching modes
• Brand identity is unclear and inconsistent
• Difficult to establish coherent design system

Options

1. Extend cyberpunk to all modes: Dark theme with neon accents throughout
2. Align Card Deck to Corporate Blue: Use standard styling, remove gradients
3. Explicit mode skins: Create visually distinct "skins" with clear labels

Acceptance Criteria

• Chosen unification strategy documented
• Visual design applied consistently across all three modes
• No jarring transitions when switching between modes
• Theme name and palette updated in copilot-instructions.md