Split monolithic script into focused modules

Refactored the single 1200-line es24n_conf.py into six modules plus a
slim entry point, in preparation for the upcoming network-based config
workflow. Each file has a clear, single responsibility:

  ui.py              — ANSI colours, display primitives, input prompts
  serial_port.py     — SerialPort class (termios/fcntl/select)
  models.py          — IOMConfig and ShelfConfig dataclasses
  redfish.py         — Redfish API client (shared by all workflows)
  workflow_serial.py — Serial-based IOM network configuration workflow
  workflow_firmware.py — IOM and Fabric Card firmware update workflow
  es24n_conf.py      — Entry point and main menu only

No functional changes. All imports verified.

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

ui.py

@@ -0,0 +1,120 @@
+"""
+ui.py — ANSI colour helpers, display primitives, and input prompts.
+Shared by all ES24N workflows.
+"""
+
+import ipaddress
+import sys
+
+
+# ── ANSI colour helpers ───────────────────────────────────────────────────────
+class C:
+    RED   = "\033[0;31m"
+    GRN   = "\033[0;32m"
+    YEL   = "\033[1;33m"
+    CYN   = "\033[0;36m"
+    WHT   = "\033[1;37m"
+    DIM   = "\033[2m"
+    BOLD  = "\033[1m"
+    RESET = "\033[0m"
+    CLEAR = "\033[2J\033[H"
+
+
+def _c(colour: str, text: str) -> str:
+    return f"{colour}{text}{C.RESET}"
+
+
+def info(msg: str):  print(f"  {_c(C.CYN,  'i')}  {msg}")
+def ok(msg: str):    print(f"  {_c(C.GRN,  'OK')} {msg}")
+def warn(msg: str):  print(f"  {_c(C.YEL,  '!')}  {msg}")
+def error(msg: str): print(f"  {_c(C.RED,  'X')}  {msg}")
+
+
+def banner():
+    print(C.CLEAR, end="")
+    w = 60
+    print(_c(C.CYN, "  +" + "-" * w + "+"))
+    print(_c(C.CYN, "  |") + _c(C.WHT + C.BOLD,
+          "      TrueNAS ES24N IOM Configuration Tool          ") + _c(C.CYN, "  |"))
+    print(_c(C.CYN, "  |") + _c(C.DIM,
+          "  Serial Config & Firmware Updates  (stdlib only)   ") + _c(C.CYN, "  |"))
+    print(_c(C.CYN, "  +" + "-" * w + "+"))
+    print()
+
+
+def rule(title: str = ""):
+    width = 60
+    if title:
+        pad   = max(0, width - len(title) - 2)
+        left  = pad // 2
+        right = pad - left
+        line  = f"{'-' * left} {title} {'-' * right}"
+    else:
+        line = "-" * width
+    print(f"\n  {_c(C.YEL, line)}\n")
+
+
+def draw_table(headers: list, rows: list, col_widths: list):
+    sep = "  +-" + "-+-".join("-" * w for w in col_widths) + "-+"
+
+    def fmt_row(cells):
+        return "  | " + " | ".join(
+            str(c).ljust(w) for c, w in zip(cells, col_widths)
+        ) + " |"
+
+    print(_c(C.DIM, sep))
+    print(_c(C.BOLD, fmt_row(headers)))
+    print(_c(C.DIM, sep))
+    for row in rows:
+        print(fmt_row(row))
+    print(_c(C.DIM, sep))
+
+
+def draw_box(lines: list, colour: str = C.CYN):
+    width = max(len(l) for l in lines) + 4
+    print(f"  {_c(colour, '+' + '-' * width + '+')}")
+    for line in lines:
+        pad = width - len(line) - 2
+        print(f"  {_c(colour, '|')}  {line}{' ' * pad}  {_c(colour, '|')}")
+    print(f"  {_c(colour, '+' + '-' * width + '+')}")
+
+
+# ── Input helpers ─────────────────────────────────────────────────────────────
+def prompt(label: str, default: str = "") -> str:
+    display = f"  {_c(C.CYN, label)}"
+    if default:
+        display += f" {_c(C.DIM, f'[{default}]')}"
+    display += ": "
+
+    sys.stdout.write(display)
+    sys.stdout.flush()
+    val = sys.stdin.readline().strip()
+    return val if val else default
+
+
+def prompt_ip(label: str) -> str:
+    while True:
+        val = prompt(label)
+        try:
+            ipaddress.IPv4Address(val)
+            return val
+        except ValueError:
+            warn(f"'{val}' is not a valid IPv4 address — please try again.")
+
+
+def prompt_yn(label: str, default: bool = True) -> bool:
+    hint = "Y/n" if default else "y/N"
+    val  = prompt(f"{label} [{hint}]").strip().lower()
+    if not val:
+        return default
+    return val in ("y", "yes")
+
+
+def prompt_password() -> str:
+    while True:
+        val = prompt(
+            "Admin password (BMC/chassis serial, e.g. MXE3000043CHA007)",
+        )
+        if val:
+            return val
+        warn("Password cannot be empty.")