Add comprehensive architecture documentation for distributed systems and microservices

[Copilot]

This PR adds comprehensive architecture documentation to the /docs/architecture directory, addressing the missing documentation files referenced in the existing index.md. The implementation focuses on creating detailed, practical guides for software architects and developers.

What was added

Distributed Systems Architecture (distributed-systems.md)

• Theoretical foundations: CAP theorem, ACID vs BASE properties, consensus algorithms
• Communication patterns: Synchronous (HTTP/REST, gRPC) and asynchronous (message queues, event streaming)
• Data management: Partitioning strategies, distributed transactions, saga patterns
• Implementation examples: Raft consensus in Go, Redis clustering, Kafka event streaming
• Monitoring and observability: Distributed tracing with OpenTelemetry, metrics collection

Microservices Architecture (microservices.md)

• Core principles: Service independence, domain-driven design, bounded contexts
• Design patterns: Service decomposition strategies, API gateway implementation
• Communication: Event-driven architecture, CQRS pattern, service mesh with Istio
• Testing strategies: Unit testing, integration testing with containers, contract testing with Pact
• Security: JWT authentication, rate limiting, input validation
• Deployment: Kubernetes configurations, Helm charts, auto-scaling

Key features

Each documentation file includes:

• Theoretical concepts with clear explanations
• Code examples in multiple languages (Python, Java, Go, TypeScript)
• Configuration samples for real-world deployment scenarios
• Best practices for production environments
• Security considerations throughout
• Practical use cases like e-commerce platform architecture

The documentation follows the same format and structure as the existing fundamentals.md file, ensuring consistency across the architecture guide.

Examples of practical implementations

The distributed systems documentation includes working examples of:

# Saga pattern for distributed transactions
class OrderSaga:
    def execute(self, order_request):
        try:
            reservation = self.inventory_service.reserve_items(order_request.items)
            payment = self.payment_service.charge_customer(order_request)
            order = self.order_service.create_order(order_request)
            return order
        except Exception as e:
            # Execute compensation actions in reverse order
            self.compensate_saga(correlation_id, e)

The microservices documentation provides complete API gateway implementations, service mesh configurations, and comprehensive testing strategies for distributed systems.

Remaining work

This PR addresses 2 of the 5 missing architecture documentation files. The remaining files (api-design.md, performance-scalability.md, security.md) will be added in subsequent work to complete the comprehensive architecture documentation set.

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