v1.2.0 - Headless-First Architecture & Trilingual Docs

What's New in v1.2.0

• 🛡️ 100% Headless-First Engine: Pure business logic core with zero UI requirements. Complete freedom to build custom UI or export to Flutter/React Native bridges.
• 🔌 Pluggable Evaluation Strategy: AppUpdateEvaluator protocol for custom rollout rules, grace periods, and major/minor version diffs.
• 📦 Codable & Metadata Support: AppVersion and AppUpdateAction conform to Codable; AppUpdateConfig parses arbitrary custom backend metadata.
• ⚡️ Swift 6 Concurrency & Task Deduplication: Concurrency-safe closures and simultaneous check deduplication.
• 🎨 SVG Vector Banner: Crisp dark-mode branded vector banner in art/banner.svg.
• 🌍 Trilingual Documentation: Complete documentation in English, Tiếng Việt, and 日本語.