fix: route windows start through cross-platform entry

[RuoqianXu]

Summary

• route pnpm start through scripts/start-entry.mjs so Windows uses the PowerShell startup path instead of a Unix-only shell script
• update README and setup guides in English and Chinese to explain the platform-specific pnpm start behavior
• restore the quick-start note that pnpm start launches Redis, API, and Frontend services

Testing

• pnpm check:start-profile-isolation (fails on Windows because the test invokes �ash directly via spawnSync('bash', ...))