docs: add comprehensive frontend landing page plan and download design skills

Add detailed landing page development plan in docs/frontend_landing_plan.md:
- Complete landing page structure (Hero, Problem/Solution, Features, Demo, CTA)
- Design guidelines from downloaded skills (typography, color, motion, composition)
- Security considerations (XSS prevention, input sanitization, CSP)
- Performance targets (LCP <2.5s, bundle <150KB, Lighthouse >90)
- Responsiveness and accessibility requirements (WCAG 2.1 AA)
- Success KPIs and monitoring setup
- 3-week development timeline with daily tasks
- Definition of Done checklist

Download 10+ frontend/UI/UX skills via universal-skills-manager:
- frontend-ui-ux: UI/UX design without mockups
- frontend-design-guidelines: Production-grade interface guidelines
- frontend-developer: React best practices (40+ rules)
- frontend-engineer: Next.js 14 App Router patterns
- ui-ux-master: Comprehensive design systems and accessibility
- ui-ux-systems-designer: Information architecture and interaction
- ui-ux-design-user-experience: Platform-specific guidelines
- Plus additional reference materials and validation scripts

Configure universal-skills MCP with SkillsMP API key for curated skill access.

Safety first: All skills validated before installation, no project code modified.

Refs: Universal Skills Manager (github:jacob-bd/universal-skills-manager)
Next: Begin Sprint 3 landing page development

.opencode/skills/ui-ux-master/references/accessibility.md

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+# Accessibility Guidelines
+
+Complete WCAG compliance guide and accessibility best practices.
+
+## WCAG 2.1 Levels
+
+**Level A (Minimum):**
+- Basic accessibility features
+- Text alternatives for images
+- Keyboard accessible
+
+**Level AA (Standard):**
+- 4.5:1 contrast for text
+- Resize text to 200%
+- Focus visible
+- **Most websites target AA**
+
+**Level AAA (Enhanced):**
+- 7:1 contrast for text
+- Audio descriptions for video
+- Sign language for audio
+
+## Quick Checklist
+
+✅ Alt text for images
+✅ Keyboard navigable (Tab, Enter, Esc, Arrows)
+✅ Focus visible (outline or custom)
+✅ Color contrast meets AA (4.5:1 text, 3:1 UI)
+✅ Headings in logical order (h1 → h2 → h3)
+✅ ARIA labels for interactive elements
+✅ Forms have labels
+✅ Error messages clear and helpful
+✅ Reduce motion respected
+✅ Screen reader tested
+
+## Testing Tools
+
+- **axe DevTools** (browser extension)
+- **WAVE** (web accessibility evaluation)
+- **Lighthouse** (Chrome DevTools)
+- **Screen readers:** NVDA (Win), VoiceOver (Mac/iOS), JAWS (Win)
+
+---
+
+*See SKILL.md for implementation details*