feat: add Camoufox browser runtime support

[harshit0605]

Summary

Adds optional Camoufox browser runtime support to Crawl4AI while keeping the PR scoped to the upstream-ready core runtime, docs, and tests.

• introduces browser_runtime="camoufox" and camoufox_options on BrowserConfig
• integrates Camoufox launch and persistent-context flows into BrowserManager
• validates unsupported combinations up front, including persistent Camoufox + storage_state
• adds documentation, examples, and focused regression/unit coverage for the new runtime
• intentionally excludes Docker and Coolify deployment changes so the review stays focused on the library/runtime contribution

List of files changed and why

• crawl4ai/async_configs.py, crawl4ai/async_crawler_strategy.py, crawl4ai/browser_manager.py - add the Camoufox runtime path, config validation, and runtime-specific browser handling.
• pyproject.toml, uv.lock - add the optional Camoufox extra and refresh the lockfile.
• docs/examples/camoufox_example.py, docs/examples/camoufox_proxy_example.py - add runnable examples for dedicated, persistent, and proxy-backed Camoufox usage.
• docs/md_v2/advanced/camoufox-browser.md, docs/md_v2/core/browser-crawler-config.md, docs/md_v2/core/examples.md, mkdocs.yml - document the runtime, surface it in navigation, and link the new examples.
• tests/unit/test_camoufox_runtime.py, tests/regression/test_reg_camoufox.py - cover runtime validation/launch behavior and exercise the integration path with tighter skip conditions for missing local runtime prerequisites.

How Has This Been Tested?

• uv run --with pytest --with pytest-asyncio pytest -q tests/unit/test_camoufox_runtime.py tests/regression/test_reg_camoufox.py

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