Use default-jdk-headless on python:slim instead of temurin:alpine

ARM64 has no eclipse-temurin:17-jdk-alpine manifest. Switch to the
Debian-based python:3.11-slim and install OpenJDK via apt so the
image builds on both Mac Mini (ARM) and x86_64 hosts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

timetable-solver-service/Dockerfile

@@ -1,19 +1,15 @@
-# Timetable solver — Timefold needs a JVM at runtime, so this image bundles
-# OpenJDK 17 alongside Python 3.11.
-FROM eclipse-temurin:17-jdk-alpine AS jdk
-
+# Timetable solver — Timefold needs a JVM at runtime (it's a JPype wrapper
+# around the Java engine). We install OpenJDK 17 alongside Python 3.11 on
+# the slim Debian base so the same image works on ARM64 and x86_64.
 FROM python:3.11-slim
 
-# Pull the JVM from the temurin image so we don't shell out to apt for a JDK
-# (which on slim adds ~400 MB).
-COPY --from=jdk /opt/java/openjdk /opt/java/openjdk
-ENV JAVA_HOME=/opt/java/openjdk
+ENV JAVA_HOME=/usr/lib/jvm/default-java
 ENV PATH="${JAVA_HOME}/bin:${PATH}"
 
 WORKDIR /app
 
-# Install runtime deps the JVM bridge needs.
 RUN apt-get update && apt-get install -y --no-install-recommends \
+        default-jdk-headless \
         libgomp1 \
     && rm -rf /var/lib/apt/lists/*
 
@@ -24,7 +20,7 @@ COPY app ./app
 
 EXPOSE 8095
 
-HEALTHCHECK --interval=30s --timeout=5s --start-period=30s --retries=3 \
+HEALTHCHECK --interval=30s --timeout=5s --start-period=60s --retries=3 \
     CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8095/health')" || exit 1
 
 CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8095"]