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/frontend-developer/references/vue-nuxt.md

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+# Vue & Nuxt 3 Architecture
+
+**Status**: Definitive Guide
+**Stack**: Vue 3 (Composition API), Nuxt 3
+
+## 🏗 Architecture: Composition & Modules
+
+### 1. Composition API Only
+
+- **Ban**: Options API (`data`, `methods`).
+- **Enforce**: `<script setup lang="ts">`.
+- **Why**: Better TypeScript support, logic reuse via composables.
+
+### 2. Nuxt Directory Structure
+
+```
+server/              # API routes (Nitro)
+components/          # Auto-imported components
+composables/         # Auto-imported logic
+pages/               # File-based routing
+layouts/             # Layouts
+stores/              # Pinia definitions
+```
+
+## ⚡ Performance Patterns
+
+### 1. Data Fetching
+
+- **SSR-Friendly**: Use `useFetch` or `useAsyncData`.
+- **Keying**: Always provide a unique key if parameters change.
+- **Lazy**: `lazy: true` to prevent blocking navigation.
+
+```ts
+// ✅ GOOD
+const { data, pending } = await useFetch("/api/posts", {
+  lazy: true,
+  server: false, // If client-only execution is needed
+});
+```
+
+### 2. State Management (Pinia)
+
+- **Setup Stores**: Use the function syntax (like `setup()`), not the object syntax.
+- **Dedupe**: Don't put everything in store. Use `useState` for simple shared state.
+
+### 3. Compute Stability
+
+- Use `computed()` for derived state.
+- Use `shallowRef()` for large objects that don't need deep reactivity.
+
+## 🧪 Testing
+
+- **Unit**: Vitest.
+- **Component**: Vue Test Utils.
+- **E2E**: Nuxt Test Utils (Playwright wrapper).