feat: add langflow-sdk support to release workflow (#12679)

* feat: add langflow-sdk build and publish support to release workflow

Add support for building and publishing the langflow-sdk package in the
release workflow, mirroring the nightly build support added in #12491.

Changes:
- Add `release_sdk` workflow input for controlling SDK release
- Add `determine-sdk-version` job with first-release PyPI handling
- Add `build-sdk` job with version verification and import testing
- Add `publish-sdk` job that publishes SDK to PyPI before LFX
- Update `build-lfx` to download SDK artifact and test both wheels together
- Update `build-base` and `build-main` to use SDK wheel as find-links
- Pass SDK artifact to cross-platform tests
- Add validation: releasing LFX requires releasing SDK
- Add pre-release version handling for SDK and LFX's SDK dependency

* Update release.yml

* Update release.yml

* Potential fix for pull request finding

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* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

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