chore: mypy lint

semantic_router/encoders/__init__.py

semantic_router/encoders/bm25.py

semantic_router/index/base.py

semantic_router/index/hybrid_local.py

semantic_router/index/local.py

semantic_router/index/pinecone.py

semantic_router/index/postgres.py

semantic_router/index/qdrant.py

semantic_router/routers/base.py

semantic_router/routers/hybrid.py

semantic_router/schema.py

tests/unit/test_hybrid_layer.py