IBM DB2 vector store documentation addition

[yiweiHeOSS]

This PR is for the documentation addition of DB2.

IBM DB2 relational database supports vector store and vector search in version v12.1.2 and above. This PR is to implement LangChain vector store and vector search support with DB2.

The source code will be delivered to https://github.com/langchain-ai/langchain-ibm via langchain-ai/langchain-ibm#68, and a Pypi package langchain-db2 will be published in https://pypi.org/project/langchain-db2/

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Name	Status	Preview	Comments	Updated (UTC)
langchain	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 27, 2025 6:34pm

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #31008 will not alter performance

_{Comparing yiweiHeOSS:addDocDB2VS (d5d8377) with master (9f17fab)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched benchmarks

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #31008 will not alter performance

_{Comparing yiweiHeOSS:addDocDB2VS (d5d8377) with master (9f17fab)}

Summary

✅ 14 untouched benchmarks

[yiweiHeOSS]

Hi @ccurme, could you please review this PR? I tried to fix the format requirements. Thanks.

[yiweiHeOSS]

Hi @ccurme. Could you please review this PR? Thank you so much! If you are busy, can you let someone else review it if it is ok?

[MateuszOssGit]

LGTM

[MateuszOssGit]

@yiweiHeOSS Please resolve conflicts on your branch