[Docs] Document Service Architecture & Event Flow #18

Missing Information

• Service communication diagram
• Event flow between services
• Message format documentation
• Error handling paths

Solution

Create architecture documentation:

• Service diagram (6 services + dependencies)
• Event flow for emergency workflow
• Message format specs
• Fallback behavior

Files to Create

• ARCHITECTURE.md (root directory)
• Include mermaid sequence diagrams

Acceptance Criteria

• Service diagram with ports
• Event flow sequences documented
• Message format examples
• Failure handling paths