fix: Correct data paths and embeddings fallback for production deployment

backend/embeddings.py

@@ -155,10 +155,14 @@ class EmbeddingGenerator:
                 return np.array(response.embeddings[0])
             except Exception as e:
                 print(f"Cohere query embedding error: {e}")
-                # Fallback to sentence transformer
-                return self.sentence_model.encode([query], convert_to_numpy=True)[0]
+                # Fallback to simple embeddings
+                return self._simple_text_to_vector(query)
         else:
-            return self.sentence_model.encode([query], convert_to_numpy=True)[0]
+            if self.sentence_model is not None:
+                return self.sentence_model.encode([query], convert_to_numpy=True)[0]
+            else:
+                # Use simple hash-based embeddings
+                return self._simple_text_to_vector(query)
     
     def compute_similarity(self, embedding1: np.ndarray, embedding2: np.ndarray) -> float:
         """Compute cosine similarity between two embeddings"""