Add vector store configuration to API

[Beastmaster23]

Description

Introduces VectorStoreConfig and VectorStoreProvider models(classes), updates configuration schema to support vector store settings, and adds endpoints for getting and updating vector store configuration. Ensures default vector store config is set if missing and integrates vector store management alongside LLM and embedder configurations.

Fixes #3444

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes Fix: Openmemory run.sh non-existent vector-store route #3444
• Made sure Checks passed

[CLAassistant]

All committers have signed the CLA.