docs: add ZeusDB vector store integration (#32822)

## Description

This PR adds documentation for the new ZeusDB vector store integration
with LangChain.

## Motivation

ZeusDB is a high-performance vector database (Python/Rust backend)
designed for AI applications that need fast similarity search and
real-time vector ops. This integration brings ZeusDB's capabilities to
the LangChain ecosystem, giving developers another production-oriented
option for vector storage and retrieval.

**Key Features:**
- **User-Friendly Python API**: Intuitive interface that integrates
seamlessly with Python ML workflows
- **High Performance**: Powered by a robust Rust backend for
lightning-fast vector operations
- **Enterprise Logging**: Comprehensive logging capabilities for
monitoring and debugging production systems
- **Advanced Features**: Includes product quantization and persistence
capabilities
- **AI-Optimized**: Purpose-built for modern AI applications and RAG
pipelines

## Changes

- Added provider documentation:
`docs/docs/integrations/providers/zeusdb.mdx` (installation, setup).

- Added vector store documentation:
`docs/docs/integrations/vectorstores/zeusdb.ipynb` (quickstart for
creating/querying a ZeusDBVectorStore).

- Registered langchain-zeusdb in `libs/packages.yml` for discovery.

## Target users

- AI/ML engineers building RAG pipelines

- Data scientists working with large document collections

- Developers needing high-throughput vector search

- Teams requiring near real-time vector operations

## Testing

- Followed LangChain's "How to add standard tests to an integration"
guidance.
- Code passes format, lint, and test checks locally.
- Tested with LangChain Core 0.3.74
- Works with Python 3.10 to 3.13

## Package Information
**PyPI:** https://pypi.org/project/langchain-zeusdb
**Github:** https://github.com/ZeusDB/langchain-zeusdb

libs/packages.yml

@@ -735,6 +735,10 @@ packages:
 - name: langchain-google-bigtable
   name_title: Bigtable
   repo: googleapis/langchain-google-bigtable-python
+- name: langchain-oci
+  name_title: Oracle Cloud Infrastructure (OCI)
+  repo: oracle/langchain-oracle
+  path: .
 - name: langchain-timbr
   provider_page: timbr
   path: .
@@ -742,7 +746,6 @@ packages:
 - name: langchain-zenrows
   path: .
   repo: ZenRows-Hub/langchain-zenrows
-- name: langchain-oci
-  name_title: Oracle Cloud Infrastructure (OCI)
-  repo: oracle/langchain-oracle
-  path: .
+- name: langchain-zeusdb
+  repo: zeusdb/langchain-zeusdb
+  path: libs/zeusdb