Add ical_value property to vDuration

[xxiaoxiong]

This PR adds the ical_value property to vDuration, contributing to Issue #876.

Changes

• Added ical_value property to vDuration (src/icalendar/prop/dt/duration.py)
  • Returns: timedelta - The duration as a timedelta object
  • Type hint: timedelta
  • RFC reference: :rfc:5545#section-3.3.6
  • Includes comprehensive docstring with examples

Tests

• Created test_vDuration.py with 6 comprehensive test cases:
  • test_ical_value_basic - Tests basic timedelta return
  • test_ical_value_components - Tests days/seconds components
  • test_ical_value_from_ical - Tests with parsed ical strings
  • test_ical_value_negative - Tests negative durations
  • test_ical_value_zero - Tests zero duration
  • test_ical_value_from_string - Tests vDuration created from string
• All tests pass: 6 passed

Quality Checks

• Add type hint
• Add docstring with RFC reference
• Add tests for all code paths
• Pass ruff format check
• Pass ruff lint check
• All tests pass

Relates to #876

[read-the-docs-community]

Documentation build overview

📚 icalendar | 🛠️ Build #32600448 | 📁 Comparing 14f429b against latest (7357cec)

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5 files changed · ± 5 modified

± Modified

• 404.html
• genindex.html
• reference/api/icalendar.prop.dt.duration.html
• reference/api/icalendar.prop.dt.html
• _modules/icalendar/prop/dt/duration.html

[stevepiercy]

@xxiaoxiong thank you for opening this PR. Because you haven't responded to the reviews and CI failures, I'm closing all of your PRs to let other contributors know that they are free to work on it. You're welcome to address our comments, resolve the matters, and reopen your pull request at any time, specifically to address the question of AI usage and add a change log, per Contribute. Thank you!