fix(docker): make deep-crawl streaming mirror Python library behaviour

[SohamKukreti]

Summary

Changes made in the PR:

• Route deep-crawl stream=True requests with a single URL through AsyncWebCrawler.arun so each discovered page is streamed as its own CrawlResult
• Preserve existing arun_many + MemoryAdaptiveDispatcher behavior for non–deep-crawl or multi-URL streaming.
• Add Docker REST tests for deep-crawl streaming success (single URL) and helpful error on multi-URL usage

Fixes: (#1779)

List of files changed and why

deploy/docker/api.py: Mirror python library deep crawl stream behaviour in handle_stream_crawl_request()
tests/docker/test_rest_api_deep_crawl.py: Add test for deep crawl stream behaviour

How Has This Been Tested?

Built and ran the docker container, ran custom example script and created new tests for testing functionality.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added/updated unit tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes