chore: add release automation

[piotr-iohk]

This PR adds release process automation for bitkit-ios:

1. Adds a /release command (Claude Code + Cursor) that handles version bumping, release branch creation, PR, tagging, draft GitHub release, store release notes generation, and optional CLI build+upload to TestFlight
2. Adds Docs/RELEASE.md documenting the full release lifecycle from branch creation through post-release
3. Adds ExportOptions.plist for CLI-based archive and App Store Connect uploads

Description

The /release command mirrors the existing Android release flow, adapted for iOS:

• Reads version from project.pbxproj, prompts for bump type (patch/minor/major)
• For patch releases, supports branching from a previous tag with cherry-picked commits
• Bumps MARKETING_VERSION and CURRENT_PROJECT_VERSION across all app targets via sed
• Creates release branch, version bump PR, tag, and draft GitHub release
• Generates translated store release notes (EN/FR/ES/PT/DE) from the changelog
• Optionally archives and uploads to TestFlight via CLI (xcodebuild + xcrun altool)

Linked Issues/Tasks

N/A

Screenshot / Video

N/A

Made with Cursor