fix(api): lint errors in Rate Limiter + RAG services

- Remove unused imports (settings, uuid)
- Add 'from e' to exception raises (B904)
- Add strict=True to zip() (B905)
- Remove unused variable

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/services/embedding_service.py

@@ -143,19 +143,19 @@ class OllamaEmbeddingService:
 
             return embedding
 
-        except httpx.TimeoutException:
+        except httpx.TimeoutException as e:
             logger.error("embedding_timeout", model=self._model, text_len=len(text))
-            raise EmbeddingError(f"Embedding timeout after {self._timeout}s")
+            raise EmbeddingError(f"Embedding timeout after {self._timeout}s") from e
         except httpx.HTTPStatusError as e:
             logger.error(
                 "embedding_http_error",
                 status=e.response.status_code,
                 model=self._model,
             )
-            raise EmbeddingError(f"Ollama API error: {e.response.status_code}")
+            raise EmbeddingError(f"Ollama API error: {e.response.status_code}") from e
         except Exception as e:
             logger.error("embedding_error", error=str(e), model=self._model)
-            raise EmbeddingError(f"Embedding failed: {e}")
+            raise EmbeddingError(f"Embedding failed: {e}") from e
 
     async def embed_batch(
         self,