feat: add custom embedding types and migrate providers

- introduce baseembeddingsprovider and helper for embedding functions  
- add core embedding types and migrate providers, factory, and storage modules  
- remove unused type aliases and fix pydantic schema error  
- update providers with env var support and related fixes

src/crewai/rag/embeddings/providers/roboflow/roboflow_provider.py

@@ -0,0 +1,25 @@
+"""Roboflow embeddings provider."""
+
+from chromadb.utils.embedding_functions.roboflow_embedding_function import (
+    RoboflowEmbeddingFunction,
+)
+from pydantic import Field
+
+from crewai.rag.core.base_embeddings_provider import BaseEmbeddingsProvider
+
+
+class RoboflowProvider(BaseEmbeddingsProvider[RoboflowEmbeddingFunction]):
+    """Roboflow embeddings provider."""
+
+    embedding_callable: type[RoboflowEmbeddingFunction] = Field(
+        default=RoboflowEmbeddingFunction,
+        description="Roboflow embedding function class",
+    )
+    api_key: str = Field(
+        default="", description="Roboflow API key", validation_alias="ROBOFLOW_API_KEY"
+    )
+    api_url: str = Field(
+        default="https://infer.roboflow.com",
+        description="Roboflow API URL",
+        validation_alias="ROBOFLOW_API_URL",
+    )