Add System Check workflow with serial and network connection options

Adds workflow_check.py: a read-only diagnostic that queries current network
settings and firmware versions (IOM + Fabric Card) from both IOMs. Accessible
via a new main menu option (3 — System Check); Exit moves to option 4.
Supports both serial console (curl over the serial session) and direct network
(HTTPS to management IP) connection methods.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

es24n_conf.py

@@ -22,6 +22,7 @@ import time
 sys.path.insert(0, os.path.join(os.path.dirname(os.path.abspath(__file__)), "modules"))
 
 from ui import _c, C, banner, draw_box, ok, warn, prompt
+from workflow_check import system_check_workflow
 from workflow_firmware import firmware_update_workflow
 from workflow_serial import configure_shelf
 
@@ -32,11 +33,12 @@ def main():
         draw_box([
             f"  {_c(C.BOLD, '1')}  Configure a new ES24N shelf  (serial)",
             f"  {_c(C.BOLD, '2')}  Update IOM / Fabric Card Firmware",
-            f"  {_c(C.BOLD, '3')}  Exit",
+            f"  {_c(C.BOLD, '3')}  System Check",
+            f"  {_c(C.BOLD, '4')}  Exit",
         ])
         print()
 
-        choice = prompt("Select [1/2/3]")
+        choice = prompt("Select [1/2/3/4]")
         if choice == "1":
             another = configure_shelf()
             if not another:
@@ -44,9 +46,11 @@ def main():
         elif choice == "2":
             firmware_update_workflow()
         elif choice == "3":
+            system_check_workflow()
+        elif choice == "4":
             break
         else:
-            warn("Please enter 1, 2, or 3.")
+            warn("Please enter 1, 2, 3, or 4.")
             time.sleep(1)
 
     print()