pickling doesn't preserve DST offset

[ruaridhw]

• I am on the latest Pendulum version.
• I have searched the issues of this repo and believe that this is not a duplicate.

• OS version and name: macOS 15.5
• Pendulum version: 3.2.0.dev0 2adcc02

Issue

The following test case fails for after_fold because pendulum doesn't keep a record of which side of the fold this datetime is. It only knows the date, time, and "Chicago"...

chicago_tz = pendulum.timezone('America/Chicago')
before_fold = pendulum.datetime(2024, 11, 3, 6, 0, 0, tz='utc').astimezone(chicago_tz)
after_fold = pendulum.datetime(2024, 11, 3, 7, 0, 0, tz='utc').astimezone(chicago_tz)

for test_dt in [before_fold, after_fold]:
    pickled_data = pickle.dumps(test_dt)
    unpickled_dt = pickle.loads(pickled_data)

    assert test_dt.timestamp() == unpickled_dt.timestamp()

[ruaridhw]

Raised PR here. If this is of interest I can finish the PR (add tests, docs etc)