Switch Docker base from alpine to debian-slim for torch compatibility

torch/sentence-transformers only provide manylinux (glibc) wheels,
not musl. The musl-compiled tori binary is statically linked and
runs fine on glibc systems.

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

Dockerfile

@@ -6,9 +6,9 @@ RUN npm ci
 COPY web/ ./
 RUN npm run build
 
-# Stage 2: Runtime
-FROM alpine:3.21
-RUN apk add --no-cache ca-certificates curl bash
+# Stage 2: Runtime (debian for glibc — torch/sentence-transformers need manylinux wheels)
+FROM debian:bookworm-slim
+RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates curl && rm -rf /var/lib/apt/lists/*
 RUN curl -LsSf https://astral.sh/uv/install.sh | sh
 ENV PATH="/root/.local/bin:$PATH"
 RUN uv venv --python 3.12 /app/venv && uv pip install --python /app/venv/bin/python sentence-transformers