fix(deps): update dependency langchain-core to v1

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
langchain-core (source, changelog)	^0.3.31 -> ^1.0.0

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

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• any of the package files in this branch needs updating, or
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The artifact failure details are included below:

File name: poetry.lock

Updating dependencies
Resolving dependencies...


Because open-learning-ai-tutor (0.2.12) depends on langchain-core (>=0.3.45,<0.4)
 and no versions of open-learning-ai-tutor match >0.2.12,<0.3.0, open-learning-ai-tutor (>=0.2.12,<0.3.0) requires langchain-core (>=0.3.45,<0.4).
So, because learn-ai depends on both langchain-core (^1.0.0) and open-learning-ai-tutor (^0.2.12), version solving failed.