fix(docker): make torch/sentence-transformers optional to unblock builds

Move torch and sentence-transformers to requirements-reranker.txt so
the main Docker build succeeds even if these large packages fail to
install. The reranker code already handles missing imports gracefully
when RERANK_ENABLED=false (the default).

This fixes the production deployment — builds were failing because of
the ~800MB torch dependency, preventing ALL new code from deploying.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-compliance/Dockerfile

@@ -10,13 +10,15 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy requirements first for better caching
-COPY requirements.txt .
+COPY requirements.txt requirements-reranker.txt ./
 
 # Create virtual environment and install dependencies
 RUN python -m venv /opt/venv
 ENV PATH="/opt/venv/bin:$PATH"
 RUN pip install --no-cache-dir --upgrade pip && \
-    pip install --no-cache-dir -r requirements.txt
+    pip install --no-cache-dir -r requirements.txt && \
+    pip install --no-cache-dir -r requirements-reranker.txt || \
+    echo "WARNING: reranker dependencies not installed (torch/sentence-transformers)"
 
 # ---- Runtime stage ----
 FROM python:3.12-slim-bookworm

backend-compliance/requirements-reranker.txt

@@ -0,0 +1,6 @@
+# Optional: Cross-Encoder Re-Ranking (CPU-only PyTorch)
+# Install separately: pip install -r requirements-reranker.txt
+# Enable at runtime: RERANK_ENABLED=true
+--extra-index-url https://download.pytorch.org/whl/cpu
+torch
+sentence-transformers>=3.0.0

backend-compliance/requirements.txt

@@ -22,10 +22,7 @@ python-multipart>=0.0.22
 # AI / Anthropic (compliance AI assistant)
 anthropic==0.75.0
 
-# Re-Ranking (cross-encoder, CPU-only PyTorch to keep image small)
---extra-index-url https://download.pytorch.org/whl/cpu
-torch
-sentence-transformers>=3.0.0
+# Re-Ranking: see requirements-reranker.txt (optional, CPU-only PyTorch)
 
 # PDF Generation (GDPR export, audit reports)
 weasyprint>=68.0