feat(v3)\!: Complete removal of deprecated litestar.contrib.sqlalchemy

This PR completes the deprecation and migration of SQLAlchemy functionality from `litestar.contrib.sqlalchemy` to `litestar.plugins.sqlalchemy`.

BREAKING CHANGE: `litestar.contrib.sqlalchemy` module has been completely removed. All imports must now use `litestar.plugins.sqlalchemy`.

Changes:
- Removed entire `litestar/contrib/sqlalchemy/` directory tree
- Updated all documentation examples to use new import paths
- Updated all tests to use new import paths
- Created proper submodule structure in `litestar/plugins/sqlalchemy/` with direct re-exports from `advanced_alchemy`
- Fixed type hint preservation for re-exported modules
- All functionality remains available through the new import structure

Migration:
- `from litestar.contrib.sqlalchemy import X` → `from litestar.plugins.sqlalchemy import X`
- `from litestar.contrib.sqlalchemy.plugins import Y` → `from litestar.plugins.sqlalchemy import Y`

Related PRs:
- litestar-org#4069 - Initial attempt by @provinzkraut
- litestar-org#4163 - Second attempt by @cofin
- litestar-org#3755 - Original deprecation PR

Closes litestar-org#4069
Closes litestar-org#4163

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: cofin

.gitignore

@@ -48,3 +48,6 @@ __pypackages__/
 certs/
 pdm.toml
 .zed
+CLAUDE.md
+CLAUDE.*.md
+todos/

docs/conf.py

@@ -147,7 +147,7 @@
     (PY_CLASS, "NoneType"),
     (PY_CLASS, "litestar._openapi.schema_generation.schema.SchemaCreator"),
     (PY_CLASS, "litestar._signature.model.SignatureModel"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.plugins.init.config.compat._CreateEngineMixin"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.plugins.init.config.compat._CreateEngineMixin"),
     (PY_CLASS, "litestar.utils.signature.ParsedSignature"),
     (PY_CLASS, "litestar.utils.sync.AsyncCallable"),
     # types in changelog that no longer exist
@@ -167,12 +167,12 @@
     (PY_CLASS, "litestar.response.RedirectResponse"),
     (PY_CLASS, "litestar.response_containers.Redirect"),
     (PY_CLASS, "litestar.response_containers.Template"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.plugins.SQLAlchemyPlugin"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.plugins.SQLAlchemySerializationPlugin"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.plugins.SQLAlchemyInitPlugin"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.dto.SQLAlchemyDTO"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.types.BigIntIdentity"),
-    (PY_CLASS, "litestar.contrib.sqlalchemy.types.JsonB"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.SQLAlchemyPlugin"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.SQLAlchemySerializationPlugin"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.SQLAlchemyInitPlugin"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.dto.SQLAlchemyDTO"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.types.BigIntIdentity"),
+    (PY_CLASS, "litestar.plugins.sqlalchemy.types.JsonB"),
     (PY_CLASS, "litestar.contrib.htmx.request.HTMXRequest"),
     (PY_CLASS, "litestar.typing.ParsedType"),
     (PY_METH, "litestar.dto.factory.DTOData.create_instance"),
@@ -220,7 +220,7 @@
     (PY_RE, r".*UserType"),
     (PY_RE, r"ModelT"),
     (PY_RE, r"litestar.*\.T"),
-    (PY_RE, r"litestar.contrib.sqlalchemy.repository.ModelT"),
+    (PY_RE, r"litestar.plugins.sqlalchemy.repository.ModelT"),
     (PY_RE, r"litestar\.middleware\.session\.base\.BaseSessionBackendT"),
     (PY_RE, r"litestar\.types.*"),
     (PY_RE, r"httpx.*"),