Fix whitelist glob expansion and auto-detect version

[ssestak]

Summary

Improves the consumer repo notification system (from PR #97) with robust branch management, stale PR handling, rollout control, and breaking change detection.

Changes

• Stable branch reuse — housekeep/bump-shared-workflows (no version suffix); if branch already exists, resets it instead of failing
• Stale PR updates — if an open PR exists from a previous version, updates its branch, title, and body instead of creating a duplicate
• Breaking change detection — major version bumps auto-create draft PRs with a CAUTION warning
• Rollout whitelist — NOTIFY_REPOS_WHITELIST repo variable with glob patterns (e.g. ios-*, one per line) controls which repos receive PRs
• Auto-detect version — workflow_dispatch picks the latest version tag automatically (no manual input)
• Robustness fixes — handles CRLF in GitHub variables, search API rate limits, set -e edge cases with gh CLI

Notes

• Requires BOT_TOKEN secret with repo + workflow scopes (classic PAT)
• Requires NOTIFY_REPOS_WHITELIST repo variable (optional) for gradual rollout
• Tested end-to-end: created PRs in futuredapp/gmlh-android and futuredapp/gmlh-ios

Test plan

• Dry run with whitelist glob patterns
• Dry run with CRLF line endings in whitelist
• CI run creating PRs in 2 whitelisted repos
• Verify stale PR update when re-running with a newer version
• Verify draft PR creation on a major version bump