Add GitHub Actions integration

[davesleal]

Description

Integrate with GitHub Actions to provide PR analysis, code reviews, and CI/CD automation directly from Slack.

Proposed Features

• Auto-post PR summaries to Slack when created
• Provide code review on demand (@SlackClaw review PR #123)
• Monitor CI/CD status and alert on failures
• Trigger deployments from Slack

Implementation Ideas

• Use GitHub webhooks to listen for PR events
• Use GitHub API to fetch PR details and files
• Integrate with existing bot_enhanced.py architecture
• Add GitHub token to environment config

Example Commands

@SlackClaw review PR #123
@SlackClaw what changed in PR #123
@SlackClaw merge PR #123 after tests pass

Benefits

• Stay in Slack for code reviews
• Faster PR feedback loop
• Centralized notifications