fix(server): register SIGTERM+SIGINT via one loop to stay under the 749-line budget

The contributor's SIGINT addition (#7315) pushed server.py to 754 lines, tripping
test_sprint10::test_server_py_under_750_lines (master was 749). Fold the two
signal.signal() try/except blocks into a single loop over (SIGTERM, SIGINT) so
SIGINT graceful shutdown lands (#7078) without growing the file past the enforced
split budget. Same _request_shutdown handler, same fail-safe on non-main-thread.

server.py

@@ -714,16 +714,11 @@ def main() -> None:
             daemon=True,
         ).start()
 
+    for _sig in (signal.SIGTERM, signal.SIGINT):  # SIGINT: Ctrl-C / ctl.sh daemons (#7078)
         try:
-        signal.signal(signal.SIGTERM, _request_shutdown)
+            signal.signal(_sig, _request_shutdown)
         except (ValueError, OSError):
-        # Not on the main thread (e.g. embedded/test harness); skip handler.
-        logger.debug("Could not install SIGTERM handler", exc_info=True)
-
-    try:
-        signal.signal(signal.SIGINT, _request_shutdown)
-    except (ValueError, OSError):
-        logger.debug("Could not install SIGINT handler", exc_info=True)
+            logger.debug("Could not install %s handler", _sig, exc_info=True)
 
     try:
         httpd.serve_forever()