Create workflow to fetch puzzle

[brendanator]

• Create GitHub workflow called fetch-puzzle.yml to fetch advent of code puzzles
• Trigger it:
  • cron - 5pm UTC between 1-25 December (12 hours after the puzzle is published)
  • workflow_dispatch - taking year and day as arguments
• Set env vars
  • AOC_SESSION: secrets.AOC_SESSION
• Add permissions needed: content, issues
• Set up
  • Check out repo - uses: actions/checkout@v4
  • Setup uv - uses astral-sh/setup-uv@v4 and uv sync
• Download the puzzle
  • Run uv run advent_of_code.py download {year} {day} and store the stdout as the part in $GITHUB_OUTPUT
• Commit and push puzzle in puzzles/year_{year}/day_{day} with user GitHub Actions
• Trigger create-puzzle-issue.yml using the year, day and part 2 as strings
  • uses: sourcery-ai/autonomous-advent-of-code/.github/workflows/create-puzzle-issue.yml@main