Fix cross-platform test and lint workflows

[QiuLsG]

Summary

• make the Playwright test command work across shells by configuring the test environment in Playwright
• enforce LF for text files so Biome checks pass on Windows checkouts
• run the lint workflow for pull requests

Testing

• pnpm check
• pnpm exec tsc --noEmit --incremental false
• pnpm build
• pnpm test --list (23 tests discovered)

The full browser suite requires the database and service credentials configured in CI.

[vercel]

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