docs: clarify Python SDK requirements and source link

[JJasonSun]

The SDK and Quickstart installation sections state that calle-ai requires Python 3.11 or later. The SDK source table links to the public Python repository, and the browser check verifies that link.

Fixes CALLE-AI/awesome-phone-call-agents#428
Fixes CALLE-AI/awesome-phone-call-agents#426

Validation:

• PyPI calle-ai 0.7.0 metadata declares Requires-Python >=3.11; the source repository is publicly accessible without authentication.
• Installed the published package with the documented pip install calle-ai command in a fresh Python 3.11.16 environment and imported CalleClient successfully. A pip target-version check rejects Python 3.10; this is a resolver check, not a Python 3.10 runtime test.
• Typecheck, build, distribution verification, and all 13 deployment tests passed using pnpm 8.10.2 and Python 3.11.16. All 22 browser checks passed across the initial run and targeted rerun; the appearance-mode check required a retry after a timeout.
• Rendered SDK and Quickstart pages were inspected; generated sdks.md, quickstart.md, and llms-full.txt contain the corrected guidance.

Only prose, a repository link, and the existing link assertion change. No API/calling example or package behavior changes; no new call test or SDK release is required. Production page verification remains pending merge and deployment.

[JJasonSun]

Production deployment succeeded: https://github.com/CALLE-AI/calle-docs/actions/runs/34947861112 (merge commit 4262016). All 386 objects were uploaded and the paginated check listed 1,088 objects.

Live SDK and Quickstart pages, both Markdown outputs, and llms-full.txt match the deployment artifact byte for byte. Browser verification confirms the Python minimum-version guidance and public source link. #426 and #428 in CALLE-AI/awesome-phone-call-agents are completed; verification comments were added and stale status labels removed.

The deployment build initially failed twice in the unchanged Calls scroll-to-top browser check. The same test passed 10 local repetitions and five delayed-script checks; the final production run passed all checks without skipping or modifying tests. The intermittent CI failure remains a separate follow-up.