Bugfix release for the CRUD write paths, route registration, and packaging. All fixes are covered by regression tests (tests/test_write_path_regressions.py).

• Body-schema leak between viewsets (critical). register() used to mutate __annotations__ of the shared class-level CRUD functions, so in any process with two or more viewsets every POST/PUT/PATCH endpoint validated against the last registered viewset's schema. Handlers are now cloned per instance before the body annotation is patched.
• PATCH is truly partial. The PATCH body is validated against an auto-generated all-optional variant of the response_model (<Schema>Patch). Previously a partial PATCH body failed validation with 422 whenever the schema had required fields.
• PATCH honors explicit null. Explicitly sent JSON null now clears a nullable column instead of being silently dropped.
• Pagination validated. Negative limit/offset are rejected with 422; limit is capped at 10000. Defaults (limit=10, offset=0) are documented.
• Filters in OpenAPI. Whitelisted ListConfig.filters fields and their __op variants (__gte, __in, …) are advertised in the generated OpenAPI schema and Swagger UI.

• PUT no longer nulls columns absent from the schema. Only fields explicitly present in the payload are written; the primary key is never overwritten. Previously PUT set every non-schema column to NULL (data loss).
• Create strips an explicit NULL primary key. Schemas with id: Optional[int] = None no longer break POST on Tortoise (id is non nullable field, but null was passed) and no longer send NULL for the PK on backends like PostgreSQL.
• Integrity violations return 409 Conflict with a sanitized message ("Integrity error: a database constraint was violated"). Raw SQL, parameters and driver internals are no longer exposed in response bodies; generic adapter errors likewise use static messages.

• Base install is now truly ORM-agnostic: SQLAlchemy and uvicorn were removed from core dependencies. The package imports cleanly without SQLAlchemy installed.
• fastapi-viewsets[sqlalchemy] now installs SQLAlchemy[asyncio], which includes greenlet — async sessions work out of the box.

• Integrity violations: 400 → 409 (message no longer contains raw SQL).
• PATCH with explicit null writes NULL (previously ignored).
• PUT no longer clears fields/columns missing from the payload.
• pip install fastapi-viewsets no longer pulls SQLAlchemy/uvicorn — use fastapi-viewsets[sqlalchemy] and install uvicorn to run apps.