feat(api): add GetContainer endpoint for Docker container retrieval

- Implemented GetContainer function to retrieve container details by ID.
- Added error handling for missing ID, container not found, and client creation failures.
- Enhanced Container struct to support omitempty for state field in JSON responses.
- Updated API documentation with Swagger annotations for the new endpoint.

internal/api/v1/docker/containers.go

@@ -16,7 +16,7 @@ type Container struct {
 	Name   string         `json:"name"`
 	ID     string         `json:"id"`
 	Image  string         `json:"image"`
-	State  ContainerState `json:"state"`
+	State  ContainerState `json:"state,omitempty" extensions:"x-nullable"`
 } // @name ContainerResponse
 
 // @x-id				"containers"