feat(ui): add comprehensive quality gates and fix linting issues

- Added ESLint, Prettier, TypeScript strict mode to ui/ directory
- Fixed 40+ lint/format issues across ui codebase
- Created extraction files for react-refresh compliance:
  - button-variants.ts for Button component styles
  - use-sidebar.ts, use-websocket-context.ts custom hooks
  - ws-context.ts WebSocket context provider
- Fixed React hooks issues (setState ordering, dependency arrays)
- Added ui:validate script to enforce quality checks
- Updated husky pre-commit to validate UI files on change

.husky/pre-commit

@@ -1,2 +1,8 @@
 # Run validation before commit (typecheck + lint + format + tests)
 bun run validate
+
+# Validate UI if changes detected
+if git diff --cached --name-only | grep -q "^ui/"; then
+  echo "[i] UI changes detected, running ui:validate..."
+  bun run ui:validate
+fi