Phase 7E: Skills and interests onboarding UI

## Phase 7E — Skills Onboarding UI ### Context Step 1 of the one-time onboarding wizard. New users define their skills so Radar can find the best matching issues. ### Design philosophy **Light. Precise. Technical. Quiet.** No marketing copy. No animations. Clean, minimal form. ### Scope Create `apps/web/src/pages/onboarding/Skills.tsx` **Fields:** - Primary languages (multi-select chips: TypeScript, Python, Go, Rust, Java, C++, Ruby, PHP...) - Frameworks (multi-select chips: React, Next.js, FastAPI, Django, Rails, Express...) - Domain interests (multi-select chips: AI/ML, DevTools, Web3, CLI, Infrastructure, Mobile...) - Experience level (radio: Beginner / Intermediate / Senior) **Validation:** - At least one language required - Experience level required - Clear error messages if empty **On submit:** Save to `profiles` table, navigate to Preferences step. ### Acceptance criteria - [ ] Component exists at `apps/web/src/pages/onboarding/Skills.tsx` - [ ] All four fields implemented - [ ] Validation prevents empty submission - [ ] Saves to `profiles` table - [ ] Follows Light/Precise/Technical/Quiet design philosophy - [ ] No placeholder text or lorem ipsum in the final output