Deployment Strategy Abstraction

**Summary**: Create a flexible deployment strategy system that allows users to choose and configure different deployment patterns for their applications.

**Acceptance Criteria**:

- [ ] Define deployment strategy configuration schema
- [ ] Support for multiple deployment strategy types (direct, slots, blue/green, canary)
- [ ] Strategy-specific configuration options
- [ ] Default strategies per Azure service type
- [ ] User override capabilities for deployment strategies
- [ ] Validation of strategy compatibility with service types
- [ ] Strategy execution engine with lifecycle hooks