Bump torch to 2.6 (transformers requires it for torch.load, CVE-2025-32434)

Dockerfile

@@ -23,7 +23,7 @@ WORKDIR /home/user/app
 
 # Install the CPU build of torch explicitly (the default PyPI wheel is CUDA and huge).
 RUN pip install --upgrade pip && \
-    pip install --user torch==2.5.1 --index-url https://download.pytorch.org/whl/cpu
+    pip install --user torch==2.6.0 --index-url https://download.pytorch.org/whl/cpu
 
 COPY --chown=user requirements.txt .
 RUN pip install --user -r requirements.txt

requirements.txt

@@ -6,7 +6,9 @@ anthropic>=0.39
 python-dotenv>=1.0
 
 # Local ML models (LINE persona analysis + history summarization)
-torch>=2.4,<2.7
+# torch >= 2.6 is required: recent transformers refuses torch.load on .bin
+# weights below 2.6 (CVE-2025-32434).
+torch>=2.6,<2.8
 transformers>=4.44,<5
 sentencepiece>=0.1.99
 numpy>=1.26