Modernize examples and OSS maintenance

[MPIsaac-Per]

What changed

• Update the Langfuse, Anthropic, OpenTelemetry, OpenAI, and LiteLLM examples to current APIs and import-safe functions.
• Harden the proxy examples with pinned container digests, loopback binding, health checks, log limits, explicit secrets, and validated key and budget inputs.
• Add a locked Python toolchain, executable tests, contributor and security policy files, release guidance, issue forms, Dependabot, CI, CodeQL, dependency review, and OpenSSF Scorecard.

Why

Several snippets performed provider work during import, used obsolete SDK patterns, or presented production configuration without failure and secret-handling controls. There was no automated way to detect drift.

Impact

Readers can import and test examples without credentials or network calls. The Docker Compose path validates from the documented fragments, and dependency/API drift is covered by CI.

Validation

• 22 pytest tests passed
• 95.65% branch coverage
• Ruff, formatter, standalone mypy checks, shellcheck, and pip-audit passed
• Docker Compose expansion passed
• actionlint passed
• zizmor pedantic online audit passed with zero findings

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