Fix serial workflow: login to IOM console and run curl for Redfish

The Redfish API at 127.0.0.1 is only accessible from within the IOM's
own shell, not directly from the host over the serial cable. The previous
approach of making urllib HTTPS requests from the host to 127.0.0.1 was
fundamentally incorrect.

Changes:
- serial_port.py: add optional per-call timeout override to
  read_until_quiet() so curl responses have enough time to arrive
- workflow_serial.py:
  - add _login_serial_console() — sends username/password over serial
    and waits for a shell prompt before proceeding
  - add _serial_redfish_request() — builds and sends a curl command
    over the serial session, parses HTTP status and JSON from the output
  - fetch_current_config(), apply_configuration(), _apply_iom() now
    accept and use a SerialPort instance via _serial_redfish_request()
  - configure_shelf() calls _login_serial_console() after collecting
    the password, before making any Redfish calls
  - remove unused _redfish_request import (HTTP transport no longer
    used in the serial workflow)

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

modules/serial_port.py

@@ -85,13 +85,15 @@ class SerialPort:
         except OSError:
             return b""
 
-    def read_until_quiet(self, quiet_period: float = 0.5) -> str:
+    def read_until_quiet(self, quiet_period: float = 0.5,
+                         timeout: Optional[float] = None) -> str:
         """
         Read until no new bytes arrive for `quiet_period` seconds,
-        or until `self.timeout` total seconds have elapsed.
+        or until `timeout` (default: self.timeout) seconds have elapsed.
+        Pass a longer timeout for operations like curl that take more time.
         """
         output   = b""
-        deadline = time.monotonic() + self.timeout
+        deadline = time.monotonic() + (timeout if timeout is not None else self.timeout)
         last_rx  = time.monotonic()
 
         while True: