docs: Add FAQ section for common questions

[meichuanyi]

Summary

This PR adds a comprehensive FAQ section to the TrustClaw README to help users understand the project and common usage scenarios.

Changes

Added ❓ Frequently Asked Questions section covering:

General

• What is TrustClaw
• Why TrustClaw over local agents (comparison table)
• What TrustClaw can do (capabilities table)

Deployment

• How to deploy (Vercel Template + CLI)
• Prerequisites
• No Anthropic/OpenAI API keys needed

Security

• OAuth security explanation
• Protection against malicious code

Tech Stack

• Technologies used (frontend/backend/database/LLM/tools)

Limitations

• Vercel Hobby plan limits (comparison table)
• Abuse prevention with rate limits

Troubleshooting

• Cron jobs not running
• Agent timeouts

Community & Support

• GitHub Issues, Contributing guide, Security contact
• Composio docs, Demo video links

License

• MIT License, free and open source

Benefits

• Helps new users quickly understand TrustClaw
• Reduces support burden with common answers
• Improves documentation completeness
• Follows documentation best practices

Testing

• Verified FAQ section renders correctly
• Checked all links are valid
• Ensured tables display properly

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This PR improves documentation quality without changing any code.