docs: add AI/ML API integration (#32430)

**Description:**
Introduces documentation notebooks for AI/ML API integration covering
the following use cases:
- Chat models (`ChatAimlapi`)
- Text completion models (`AimlapiLLM`)
- Provider usage examples
- Text embedding models (`AimlapiEmbeddings`)

Additionally, adds the `langchain-aimlapi` package entry to
`libs/packages.yml` for package management.

This PR aims to provide a comprehensive starting point for developers
integrating AI/ML API models with LangChain via the new
`langchain-aimlapi` package.

**Issue:** N/A

**Dependencies:** None

**Twitter handle:** @aimlapi

---

### **To-Do Before Submitting PR:**

* [x] Run `make format`
* [x] Run `make lint`
* [x] Confirm all documentation notebooks are in
`docs/docs/integrations/`
* [x] Double-check `libs/packages.yml` has the correct repo path
* [x] Confirm no `pyproject.toml` modifications were made unnecessarily

Co-authored-by: Mason Daugherty <mason@langchain.dev>

libs/packages.yml

@@ -726,6 +726,9 @@ packages:
   name_title: MCP Toolbox
   repo: googleapis/mcp-toolbox-sdk-python
   path: packages/toolbox-langchain
+- name: langchain-aimlapi
+  path: libs/aimlapi
+  repo: D1m7asis/langchain-aimlapi
 - name: langchain-scrapeless
   repo: scrapeless-ai/langchain-scrapeless
   path: .