Add ical_value property to vMonth

[xxiaoxiong]

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

Changes

• Added ical_value property to vMonth (src/icalendar/prop/recur/month.py)
  • Returns: int - The month number
  • Type hint: int
  • RFC reference: :rfc:5545#section-3.3.10 and :rfc:7529
  • Includes comprehensive docstring with examples
  • Supports both regular months (1-12) and leap months (e.g., "5L")
  • The int value excludes the "L" suffix; use .leap property to check leap status

Tests

• Created test_vMonth.py with 8 comprehensive test cases:
  • test_ical_value_basic - Tests basic month number
  • test_ical_value_all_months - Tests all 12 months
  • test_ical_value_leap_month - Tests leap month (RFC 7529)
  • test_ical_value_from_string - Tests string input
  • test_ical_value_from_ical - Tests parsed ical strings
  • test_ical_value_january - Tests January (1)
  • test_ical_value_december - Tests December (12)
  • test_ical_value_arithmetic - Tests arithmetic operations
• All tests pass: 8 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 #32600733 | 📁 Comparing cc6308f against latest (7357cec)

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5 files changed · ± 5 modified

± Modified

• 404.html
• genindex.html
• reference/api/icalendar.prop.recur.html
• reference/api/icalendar.prop.recur.month.html
• _modules/icalendar/prop/recur/month.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!