Cross-link SQL and Python API container services guides

[sfc-gh-amadan]

Summary

The two introductory Snowpark Container Services guides build the same example services but teach distinct implementation paths: SQL/Snowflake CLI and Snowflake Python APIs. Redirecting either to the other would remove the corresponding walkthrough.

• Add reciprocal "Choose your approach" links in each Overview so readers can select SQL/CLI or Python APIs.
• Preserve both guide URLs, walkthroughs, metadata, and assets; no redirects or retirements.
• Remove one pre-existing commented-out reference to missing assets/snowpark-ml-e2e.png in each guide. These unused references caused local validation failures.

Validation

• Both live guide URLs returned HTTP 200 before changes.
• Both guides pass local validate_guide.py with no blocking errors.
• Existing warnings remain: four in the SQL guide and six in the Python guide, concerning headings, Overview subsections, and raw HTML. Broader content updates are outside this change.
• git diff --check passed. Only these two markdown files changed.
• No tutorial code was changed or executed; no live AEM changes were made.

Test plan

• Review the new Overview paragraphs in both previews.
• Verify each cross-link opens the other guide.

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