Don't cache failed DNS lookups in the desktop client

When a laptop wakes from sleep, transient DNS resolution failures get
cached by Java's InetAddress cache. Our continuous polling loop then
hits the cached failure faster than the 10s default negative TTL can
expire, wedging the client at "connecting…" until the user restarts
it. The OS resolver is fine — `host vcell-dev.cam.uchc.edu` returns
the correct IP — but the JVM never re-queries it.

Set Security properties at the top of main(), before any DNS lookup:
- networkaddress.cache.ttl=30 (modest positive cache, matches the
  non-SecurityManager default but makes it explicit and stable)
- networkaddress.cache.negative.ttl=0 (never cache failures; recover
  immediately when DNS comes back)

Asymmetric TTL is the established pattern for long-running JVMs that
need to recover from transient DNS issues — see AWS SDK and Oracle
networking-properties guidance. Programmatic Security.setProperty is
the only reliable mechanism: -D JVM args don't bridge to security
properties, and -Dsun.net.inetaddr.ttl is undocumented in modern Java.

Observed in user log:
  >> polling failure << vcell-dev.cam.uchc.edu: nodename nor servname
  provided, or not known
  (repeating, after laptop sleep/wake)

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

Author: jcschaff

vcell-client/src/main/java/cbit/vcell/client/VCellClientMain.java

@@ -80,6 +80,14 @@ private VCellClientMain() {
      * @param args an array of command-line arguments
      */
     public static void main(java.lang.String[] args) {
+        // Recover gracefully when DNS lookups fail transiently (e.g. laptop wake from sleep).
+        // Java's default 10s negative-result cache combined with our continuous polling loop
+        // wedges the client at "connecting…" until restart, because the polling interval is
+        // shorter than the cache TTL so the cached failure never expires. A short positive
+        // TTL still gives reasonable cache locality without holding stale entries indefinitely.
+        java.security.Security.setProperty("networkaddress.cache.ttl", "30");
+        java.security.Security.setProperty("networkaddress.cache.negative.ttl", "0");
+
         System.out.println("starting with arguments " + Arrays.asList(args));
         int exitCode = 1;
         try {