Release the background resources a discarded runtime owns

Several resources outlived a disconnect on purpose, which was harmless while a
process ran exactly one session for its whole life. They are now released when
the controller itself is closed:

- the ON4KST connection supervisor thread, which stopByUser did not touch
- the sked reminder scheduler, which had no shutdown at all
- the reachability executor, whose shutdown method existed but was never called
- the PSTRotator retry scheduler and its pending retry
- the map tile proxy, whose stop method existed but was never called, leaving a
  server socket and a twelve thread pool behind
- the station map bridge listeners and its coalescing animation, which would
  otherwise keep firing into a dead user interface

These are real leaks today; they only become visible when a second runtime is
built in the same process.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hpa6bjie5qkeNG62y6FmXm

src/main/java/kst4contest/controller/On4KstConnectionManager.java

@@ -139,6 +139,20 @@ final class On4KstConnectionManager {
         scheduler.execute(() -> openConnection(token));
     }
 
+    /**
+     * Stops the supervisor thread of this manager for good.
+     *
+     * <p>{@link #stopByUser()} only ends the current ON4KST session; the periodic
+     * session monitor keeps running. That is correct while the application lives, but a
+     * manager belonging to a discarded runtime must release its thread, otherwise every
+     * operator profile switch would leave another supervisor behind holding the dead
+     * controller.</p>
+     */
+    void shutdown() {
+        scheduler.shutdownNow();
+        LOGGER.fine("ON4KST connection supervisor shut down");
+    }
+
     /**
      * Stops the current session and invalidates every scheduled callback or reconnect
      * belonging to it.