Fix from_timestamp for negative timestamps before epoch

[parinporecha]

Problem

pendulum.from_timestamp() raises on Windows 11 for timestamps earlier than approximately 12 hours before the Unix epoch (for example -43201).

Depending on the platform and Python build, the stdlib timestamp constructors can raise either OSError or OverflowError for these values.

The same underlying limitation also affects the public classmethods:

• pendulum.DateTime.fromtimestamp()
• pendulum.DateTime.utcfromtimestamp()

Reported in issue #956.

Reproduction

>>> pendulum.from_timestamp(-43200)
DateTime(1969, 12, 31, 12, 0, 0, tzinfo=Timezone('UTC'))

>>> pendulum.from_timestamp(-43201)
OSError: [Errno 22] Invalid argument

Fix

Catch (OSError, OverflowError) from the stdlib timestamp constructors and fall back to computing the result from a fixed Unix epoch plus a timedelta.

This PR covers:

• pendulum.from_timestamp()
• pendulum.DateTime.fromtimestamp()
• pendulum.DateTime.utcfromtimestamp()

The fallback preserves microseconds and keeps timezone conversion behavior intact.

Tests

Added and updated tests for:

• negative timestamps before the epoch
• explicit timezone conversion for negative timestamps
• float timestamps preserving microseconds
• forced fallback coverage for pendulum.from_timestamp()
• forced fallback coverage for DateTime.fromtimestamp()
• forced fallback coverage for DateTime.utcfromtimestamp()
• both OSError and OverflowError fallback paths

Targeted tests run locally:

PYTHONPATH=src pytest tests/datetime/test_create_from_timestamp.py -q
PYTHONPATH=src pytest tests/datetime/test_behavior.py -k 'test_fromtimestamp_falls_back_for_negative_timestamp or test_utcfromtimestamp_falls_back_for_negative_timestamp or test_fromtimestamp or test_utcfromtimestamp' -q

The full suite also passes locally on Windows 11.

[codspeed-hq]

Merging this PR will not alter performance

✅ 1 untouched benchmark

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_{Comparing parinporecha:fix/from-timestamp-negative-values (e07b164) with master (0a88aec)}