docs: Add comprehensive Files API and Vector Store integration doc (#3279)

docs: Add comprehensive Files API and Vector Store integration
documentation

- Add Files API documentation with OpenAI-compatible endpoints
- Create comprehensive guide for OpenAI-compatible file operations
- Reorganize documentation structure: move file operations to files/
directory
- Add vector store provider documentation for Milvus, SQLite-vec, FAISS
- Clean up redundant files and improve navigation
- Update cross-references and eliminate documentation duplication
- Support for release 0.2.14 FileResponse and Vector Store API features

# What does this PR do?
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relevant issues if applicable. -->

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## Test Plan
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summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->

docs/docs/api-deprecated/index.mdx

@@ -0,0 +1,62 @@
+---
+title: Deprecated APIs
+description: Legacy APIs that are being phased out
+sidebar_label: Deprecated
+sidebar_position: 1
+---
+
+# Deprecated APIs
+
+This section contains APIs that are being phased out in favor of newer, more standardized implementations. These APIs are maintained for backward compatibility but are not recommended for new projects.
+
+:::warning Deprecation Notice
+These APIs are deprecated and will be removed in future versions. Please migrate to the recommended alternatives listed below.
+:::
+
+## Migration Guide
+
+When using deprecated APIs, please refer to the migration guides provided for each API to understand how to transition to the supported alternatives.
+
+## Deprecated API List
+
+### Legacy Inference APIs
+Some older inference endpoints that have been superseded by the standardized Inference API.
+
+**Migration Path:** Use the [Inference API](../api/) instead.
+
+### Legacy Vector Operations
+Older vector database operations that have been replaced by the Vector IO API.
+
+**Migration Path:** Use the [Vector IO API](../api/) instead.
+
+### Legacy File Operations
+Older file management endpoints that have been replaced by the Files API.
+
+**Migration Path:** Use the [Files API](../api/) instead.
+
+## Support Timeline
+
+Deprecated APIs will be supported according to the following timeline:
+
+- **Current Version**: Full support with deprecation warnings
+- **Next Major Version**: Limited support with migration notices
+- **Following Major Version**: Removal of deprecated APIs
+
+## Getting Help
+
+If you need assistance migrating from deprecated APIs:
+
+1. Check the specific migration guides for each API
+2. Review the [API Reference](../api/) for current alternatives
+3. Consult the [Community Forums](https://github.com/llamastack/llama-stack/discussions) for migration support
+4. Open an issue on GitHub for specific migration questions
+
+## Contributing
+
+If you find issues with deprecated APIs or have suggestions for improving the migration process, please contribute by:
+
+1. Opening an issue describing the problem
+2. Submitting a pull request with improvements
+3. Updating migration documentation
+
+For more information on contributing, see our [Contributing Guide](../contributing/).