fix: upgrade torch to 2.5.1 for NumPy 2.x and Accelerate support

Dockerfile

@@ -29,7 +29,7 @@ COPY requirements.txt .
 # Install CPU-only PyTorch FIRST (prevents pip from pulling 2+ GB GPU wheels
 # when sentence-transformers later requests torch as a dependency).
 RUN pip install --no-cache-dir \
-    torch==2.2.2 \
+    torch==2.5.1 \
     --index-url https://download.pytorch.org/whl/cpu
 
 # Install the rest of the requirements.