feat: Add comprehensive Lip Gloss styling system for TUI

Implements complete style definitions for CodeQuest UI:
- Color palette: 12 colors optimized for light/dark terminals and RPG aesthetic
  (Primary, Secondary, Accent, Success, Warning, Error, Info, XP, Level, Quest, Magic)
- Text styles: Title, Subtitle, Heading, Body, Bold, Dim, Muted, Error, Success, Warning, Info (11 styles)
- Border styles: Rounded, Normal, Thick, Double boxes with focused/unfocused variants (7 styles)
- Progress bars: XP, Quest, and Health bars with gradient fill effects
- Status indicators: Active (green), Completed (blue), Failed (red), Pending (orange), Locked (gray)
- Interactive elements: Buttons, Inputs, Selected/Unselected items with focus states
- Special effects: Level up and quest complete notifications with decorative borders
- Layout helpers: JoinHorizontal, JoinVertical, PlaceInCenter for composition
- Rendering functions: 15+ utility functions for consistent UI rendering

All colors support both light and dark terminals. Styles follow RPG game aesthetic
with bold colors, decorative borders, and engaging visual feedback.

File: internal/ui/styles.go (522 lines)

Subagent: 12 - Lip Gloss Styles System
Phase: Development - UI Layer

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: AutumnsGrove