chore: ensure latest Xcode project settings are committed

chore: update version to 1.2.0 and set app category

fix: 降低 macOS 部署目标至 15.0，优化卡片标题处理

- 将 MACOSX_DEPLOYMENT_TARGET 从 26.2 降至 15.0，修复 macOS Sequoia 用户无法运行的问题
- 卡片标题中去除 Flomo 标签的 # 符号（如 #知识管理 → 知识管理）
- 标题超过 20 字时截断并添加省略号（…）

Update README.md

Add app icons and enhance security configuration

- Add complete set of macOS app icons (16x16 to 512x512 @1x and @2x)
- Include SVG source file and icon generation script
- Enable hardened runtime and enhanced sandbox security settings
- Disable unnecessary runtime exceptions for better security
- Update README with detailed macOS installation instructions
- Add guidance for handling Gatekeeper security warnings

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>