feat: iOS appearance, iPad logo fix, demo seed, and landing hero polish

Add System/Light/Dark preference for iPhone and iPad, restore the iPad
sidebar brand mark, ship a DEBUG seed-demo URL for rich placeholder data,
and refresh GitHub Pages with the device composite, full-bleed pale-green
hero wash, and transparent Mac screenshot chrome.

CHANGELOG.md

@@ -9,11 +9,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - **Voluntary support tip**: Settings (top of the page) includes an optional ¥28 Consumable in-app tip (StoreKit 2). All features stay free — no paywall or unlock. / **自愿打赏**：设置页顶部新增可选 ¥28 消耗型应用内打赏（StoreKit 2）。全功能仍免费，无付费墙或功能解锁。
+- **iOS appearance preference**: Settings → Preferences adds System / Light / Dark (iPhone + iPad), matching the Mac control. / **iOS 外观偏好**：设置 → 偏好设置新增跟随系统 / 浅色 / 深色（iPhone 与 iPad），与 Mac 一致。
+- **DEBUG demo seed URL**: `osgkeyboard://seed-demo` fills Home stats, History, and Dictionary with placeholder data and turns iCloud sync off (script: `scripts/seed_demo_data.py`). / **DEBUG 演示数据**：`osgkeyboard://seed-demo` 填充首页统计、历史与词库占位数据并关闭 iCloud 同步（脚本：`scripts/seed_demo_data.py`）。
 
 ### Changed
 - **Unified welcome slogan**: iPad Home now reuses the iOS onboarding brand line, and macOS onboarding shows the same “Speak it. It’s typed.” welcome slogan. / **统一欢迎口号**：iPad 首页复用 iOS 引导页品牌句，macOS 引导页也显示同一句「开口即文字。」欢迎口号。
 - **GitHub Pages landing**: redesign as a commercial product page with zh/en, light/dark, brand mark, scroll motion, and App Store screenshots; emphasizes free, cross-platform, open source, privacy, and BYOK. / **GitHub Pages 落地页**：改版为商业产品页，支持中英与日夜模式、品牌标、滚动动效与 App Store 截图；突出免费、跨端、开源、隐私与 BYOK。
 - **Landing hero device family**: Mac + iPad + iPhone nested in one mockup cluster (no outer card stroke); screens swap with language/theme. / **落地页 Hero 设备组**：Mac、iPad、iPhone 叠放在同一组设备框内（无外卡片描边）；截图随语言/主题切换。
+- **Landing hero polish**: replace CSS device frames with the marketing composite; full-bleed pale-green hero wash (no side gaps / no radial gradient); Mac story shots sit on transparent chrome. / **落地页 Hero 抛光**：设备框改为营销合成图；首屏淡绿单色通栏（无两侧留白 / 无径向渐变）；Mac 故事截图去卡片底。
+
+### Fixed
+- **iPad sidebar brand mark**: use the template `OSGLogoWide` mark with accent tint so the logo stays visible in the split-view sidebar. / **iPad 侧栏品牌标**：改用可着色的 `OSGLogoWide`，保证分栏侧栏始终显示 logo。
 
 ## [0.5.3] - 2026-07-11