Add auto-release workflow

[bguidolim]

Summary

• Adds daily automated release workflow (23:00 UTC)
• Detects production Swift changes (Sources/**/*.swift) since last tag
• Bumps MCSVersion.current, commits to main, creates and pushes tag
• Existing release.yml handles the rest (build, GitHub Release, Homebrew tap)
• Supports workflow_dispatch with a dry-run checkbox for testing

Design

• Single workflow, single job, ubuntu-latest (only git + sed needed)
• Uses a GitHub App via actions/create-github-app-token@v3 — app token pushes trigger downstream workflows (unlike GITHUB_TOKEN)
• App added as bypass actor in "Main Protection" ruleset, allowing direct push to main
• Comprehensive release summary in logs: version bump diff, included commits, changed files, and planned actions
• Idempotent: skips if tag already exists, no changes detected, or only test/non-production changes

Prerequisites (already completed)

• GitHub App created and installed on the repo
• APP_ID and APP_PRIVATE_KEY secrets configured
• App added as bypass actor in branch ruleset

Test plan

• Merge this PR
• Test via workflow_dispatch with dry-run enabled — verify summary output
• Test via workflow_dispatch with dry-run disabled — verify tag creation and release.yml trigger
• Verify skip behavior on re-run (tag already exists)