Replace direct httpx calls with shared service client architecture for
better fault tolerance, authentication, and consistency.
Changes:
- Remove httpx import and usage
- Add service client imports (inventory, production, procurement)
- Initialize service clients at module level
- Refactor all 5 dashboard endpoints to use service clients:
* health-status: Use inventory/production/procurement clients
* orchestration-summary: Use procurement/production clients
* action-queue: Use procurement client
* production-timeline: Use production client
* insights: Use inventory client
Benefits:
- Built-in circuit breaker pattern for fault tolerance
- Automatic service authentication with JWT tokens
- Consistent error handling and retry logic
- Removes hardcoded service URLs
- Better testability and maintainability