fix(FR-2200): add tsc type checking to production build (#5718)

Resolves #5716 ([FR-2200](https://lablup.atlassian.net/browse/FR-2200))

## Summary
- Add `tsc` type checking step to the production `build` script, matching `build:d` which already runs `tsc --watch`
- Add `dist/` cleanup alongside `build/web/` at the start of the build
- Fix 3 existing type errors in `src/lib/backend.ai-client-node.ts`:
  - TS2345: Add nullish coalescing for `process.env` values in `createFromEnv()`
  - TS6133: Remove unused `fields` variable in `User.create()`
  - TS7030: Add missing return value in `PipelineJob.login()`
- Add missing `@codemirror/lang-liquid` dependency required by `@codemirror/language-data`

## Test plan
- [ ] Run `pnpm run build` and verify `tsc` executes before workspace builds
- [ ] Introduce a type error and confirm the build fails at the `tsc` step
- [ ] Verify `dist/` directory is cleaned at the start of each build
- [ ] Verify no `Module not found: @codemirror/lang-liquid` error during build

🤖 Generated with [Claude Code](https://claude.com/claude-code)

[FR-2200]: https://lablup.atlassian.net/browse/FR-2200?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: nowgnuesLee

package.json

@@ -17,7 +17,7 @@
     "format-fix:i18n": "prettier --write 'resources/i18n/*.json'",
     "test": "jest",
     "wsproxy": "node ./src/wsproxy/local_proxy.js",
-    "build": "rm -rf build/web && mkdir -p build/web && pnpm run copyindex && pnpm run copyresource && pnpm run copyconfig && pnpm run -r --stream build",
+    "build": "rm -rf build/web dist && mkdir -p build/web && pnpm run copyindex && pnpm run copyresource && pnpm run copyconfig && tsc && pnpm run -r --stream build",
     "build:react-only": "pnpm run --prefix ./react build:only",
     "server:p": "serve build/web",
     "build:d": "eval \"$(node scripts/dev-config.js env)\" && node scripts/dev-config.js update && concurrently --kill-others -c \"auto\" --names \"tsc,react-relay,react\" \"tsc --watch --preserveWatchOutput\" \"cd react && pnpm run relay:watch\" \"HOST=$BAI_WEBUI_DEV_HOST BAI_WEBUI_DEV_PROXY= PORT=$BAI_WEBUI_DEV_REACT_PORT pnpm --prefix ./react run start\"",