Refuse invalid settings at start, health check follows PORT (closes #31)

A set but invalid PORT (anything but plain digits from 1 to 65535) or a relative XDG_DATA_HOME now stops the start before the database opens; before, a bad PORT left the daemon running without HTTP. entrypoint.sh refuses a MALLOC_ARENA_MAX that is not a positive whole number, since glibc ignores a bad one silently. The HEALTHCHECK probes the port PORT names, 8080 when unset. PORT is now read in internal/config, so server.New takes the config.

The README gives the real Linux state directory, lists XDG_DATA_HOME, and adds "Running under upaas": port, volume, environment, the 5g memory limit and the health check.

Unverified: the 5g memory limit could not be exercised on the build host.

Model: opus-5-5

Dockerfile

@@ -96,8 +96,8 @@ EXPOSE 8080
 
 COPY ./entrypoint.sh /entrypoint.sh
 
-# Health check using the health endpoint
+# Health check using the health endpoint, on the port PORT names
 HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
-    CMD curl -sf http://localhost:8080/.well-known/healthcheck.json || exit 1
+    CMD curl -sf "http://localhost:${PORT:-8080}/.well-known/healthcheck.json" || exit 1
 
 ENTRYPOINT ["/bin/bash", "/entrypoint.sh" ]