chore: add knip

[MarioCadenas]

Summary

Add Knip to detect and remove unused exports, dependencies, and dead code across the monorepo.

Main changes

Knip integration (knip.json, package.json, .github/workflows/ci.yml, .husky/pre-commit):
Adds Knip as a dev dependency with configuration targeting packages/appkit and packages/appkit-ui workspaces (ignoring shared, lakebase, apps, and docs). Knip runs as a CI check and as a pre-commit hook alongside lint-staged.

Dead export and code removal (across packages/appkit/src/ and packages/appkit-ui/src/):
Fixes all Knip findings by removing unused exports (making them local or prefixing with _), deleting dead files (error-boundary.tsx, table-error-boundary.tsx, lakebase-v1/utils.ts), trimming barrel re-exports (logging/index.ts, stream/index.ts, telemetry/index.ts, context/index.ts, registry/types.ts, connectors/genie/index.ts, connectors/lakebase/index.ts), and removing the FALLBACK_COLORS alias from chart constants.

Unused dependency cleanup (package.json, packages/*/package.json, apps/dev-playground/package.json):
Removes unused dependencies flagged by Knip: pg, plop, zod, date-fns, @hookform/resolvers, @tanstack/react-virtual, zod-to-ts, dependency-tree, @types/dependency-tree, @types/react-syntax-highlighter, @vitejs/plugin-react (from dev-playground). Adds missing echarts and @opentelemetry/sdk-trace-base as direct dependencies.

Other changes

• Deleted 8 auto-generated chart documentation .mdx files that were unused.
• tools/license-utils.ts — unexported functions only used locally.