fix(docker): cap FastAPI below 0.137

[nightcityblade]

Summary

Fixes #2025 by capping Docker's FastAPI dependency below 0.137, avoiding the _IncludedRouter route objects that currently trigger AttributeError in the Prometheus/FastAPI instrumentation path.

List of files changed and why

• deploy/docker/requirements.txt - Add an upper bound to FastAPI so Docker installs resolve to the last pre-0.137 release until the instrumentation compatibility issue is fixed upstream.

How Has This Been Tested?

• Ran python3 -m venv /tmp/crawl4ai-venv and /tmp/crawl4ai-venv/bin/python -m pip install --dry-run -r deploy/docker/requirements.txt to verify dependency resolution succeeds and selects fastapi-0.136.3.

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