docs(changelog): add entries for unreleased changes since 1.3.6

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: edelvalle

CHANGELOG.md

@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - **Pydantic Validator Warning**: Changed from `BeforeValidator` to `PlainValidator` for Django model field annotations to eliminate Pydantic 2.8 warning about validators returning non-self values. This is purely a technical fix with no functional changes.
+- **Query String with Model | None**: Fixed `Annotated[Model | None, Query(...)]` fields raising `TypeError: Invalid type annotation` when used in components. The `annotate_model` function now properly handles `Annotated` types by processing only the base type and flattening metadata, and `is_basic_type` now recognizes Django Model classes directly. Also fixed `_ModelPlainSerializer` to handle `None` values for optional model fields.
+
+### Changed
+- **Python 3.13**: Upgraded development environment and CI from Python 3.12 to 3.13. Bumped `uvicorn[standard]` to `>=0.34` for Python 3.13 compatibility.
+- Removed Codecov integration from CI pipeline.
 
 ## [1.3.6] - 2026-02-03