PWA: add manifest.json and iOS meta tags

[deanjstone]

• Add apps/web/public/manifest.json (name, short_name, display: standalone, start_url, theme_color/background_color matching existing light/dark values, icon entries from the icon-generation ticket).
• Add <link rel="manifest"> to apps/web/index.html.
• Add iOS-specific meta tags next to the existing apple-touch-icon line: apple-mobile-web-app-capable, apple-mobile-web-app-status-bar-style, apple-mobile-web-app-title.

Depends on the icon-generation ticket. Part of map #1.

[deanjstone]

Added `apps/web/public/manifest.json` (name/short_name "T3 Code", `display: standalone`, `start_url: /`, theme_color `#161616` / background_color `#ffffff` matching the existing boot-shell light/dark values, icon entries for the 192/512/maskable assets from #2) and wired it into `index.html`: `` plus `apple-mobile-web-app-capable`, `apple-mobile-web-app-status-bar-style` (`black-translucent`, consistent with the existing `viewport-fit=cover` safe-area handling), and `apple-mobile-web-app-title` next to the existing apple-touch-icon line.

`tsgo --noEmit` clean on `@t3tools/web`. Note: the icon files the manifest references (`pwa-192x192.png`, `pwa-512x512.png`, `maskable-icon-512x512.png`) don't have real bytes on disk yet — same macOS/Icon Composer dependency noted on #2.

Commit: 984748b on `feature/pwa-web-app`.