Add comprehensive multi-API integration support

This commit adds extensive API integration capabilities for deployment,
payments, communications, and monitoring to BlackRoad OS.

New API Integrations:
- Railway API: Cloud deployment management (GraphQL)
- Vercel API: Serverless deployment platform (REST)
- Stripe API: Payment processing and billing
- Twilio API: SMS, Voice, and WhatsApp messaging
- Slack API: Team collaboration and notifications
- Discord API: Community messaging and notifications
- Sentry API: Error tracking and application monitoring

Core Features:
- Centralized API client manager with health checking
- Comprehensive health monitoring endpoint (/api/health/*)
- Automatic retry logic and rate limit handling
- Unified status monitoring for all integrations

Infrastructure:
- Railway deployment configuration (railway.json, railway.toml)
- Enhanced GitHub Actions workflows:
  * backend-tests.yml: Comprehensive test suite with PostgreSQL/Redis
  * railway-deploy.yml: Automated Railway deployment with notifications
- Docker build validation in CI/CD pipeline

Testing:
- Comprehensive test suite for all API integrations
- API connectivity verification in CI/CD
- Mock-friendly architecture for testing without credentials

Configuration:
- Updated .env.example with all new API keys
- Added stripe and sentry-sdk to requirements.txt
- Registered all new routers in main.py
- Updated API info endpoint with new integrations

Documentation:
- API_INTEGRATIONS.md: Complete setup and usage guide
- Interactive API docs at /api/docs with all endpoints
- Health check endpoints for monitoring

All APIs are optional and gracefully handle missing credentials.
The system provides clear status messages for configuration requirements.

backend/.env.example

@@ -34,12 +34,37 @@ ENVIRONMENT=development
 # CORS (add your production domains here)
 ALLOWED_ORIGINS=http://localhost:3000,http://localhost:8000,https://blackboxprogramming.github.io,https://www.blackroad.systems
 
-# API Keys
+# API Keys - Existing Integrations
 OPENAI_API_KEY=your-openai-key-for-ai-chat
 DIGITALOCEAN_TOKEN=your-digitalocean-token
 GITHUB_TOKEN=your-github-personal-access-token
 HUGGINGFACE_TOKEN=your-huggingface-api-token
 
+# API Keys - New Deployment Platform Integrations
+RAILWAY_TOKEN=your-railway-api-token
+VERCEL_TOKEN=your-vercel-api-token
+VERCEL_TEAM_ID=your-vercel-team-id-optional
+
+# API Keys - Payment Processing
+STRIPE_SECRET_KEY=sk_test_your-stripe-secret-key
+STRIPE_PUBLISHABLE_KEY=pk_test_your-stripe-publishable-key
+
+# API Keys - Communications (SMS/WhatsApp)
+TWILIO_ACCOUNT_SID=your-twilio-account-sid
+TWILIO_AUTH_TOKEN=your-twilio-auth-token
+TWILIO_PHONE_NUMBER=+1234567890
+
+# API Keys - Team Collaboration & Notifications
+SLACK_BOT_TOKEN=xoxb-your-slack-bot-token
+SLACK_WEBHOOK_URL=https://hooks.slack.com/services/YOUR/WEBHOOK/URL
+DISCORD_BOT_TOKEN=your-discord-bot-token
+DISCORD_WEBHOOK_URL=https://discord.com/api/webhooks/YOUR/WEBHOOK/URL
+
+# API Keys - Error Tracking & Monitoring
+SENTRY_DSN=https://your-sentry-dsn@sentry.io/project-id
+SENTRY_AUTH_TOKEN=your-sentry-auth-token
+SENTRY_ORG=your-sentry-organization-slug
+
 # Blockchain & Mining
 BLOCKCHAIN_DIFFICULTY=4
 MINING_REWARD=50