PWA for iPhone and iPad: PNG icons, splash screens, manifest; stay signed in for 180 days

- iOS ignores SVG touch icons: add 120/152/167/180 apple-touch-icons, 192/512 and maskable manifest icons,
  and 25 splash screens (every iPhone size, iPad portrait+landscape incl. 12.9")
- Icons and splash screens are public so iOS can fetch them without a session
- Manifest: id, scope, categories, shortcuts; iOS standalone polish (no callout, no overscroll)
- Sessions last SESSION_DAYS (default 180) and renew daily while in use
- tools/make-icons.py regenerates the artwork

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

README.md

@@ -42,6 +42,13 @@ e.g. hub.necloud.us. Settings: `SEAFILE_URL`, `ONLYOFFICE_URL` env vars in docke
 - **Mail**: deep links to Gmail, Outlook.com, Microsoft 365 and iCloud webmail (inbox + compose).
   Providers forbid framing, and a real unified inbox would need Google/Azure app registrations.
 
+## Install on iPhone / iPad (PWA)
+
+Open the site in **Safari** (it must be the `https://` address), tap **Share -> Add to Home Screen**. The home-screen app has proper
+icons (iPhone, iPad), a splash screen for each iPhone and iPad size (including iPad Pro 12.9"), and opens full screen without Safari's bars.
+iOS keeps a separate sign-in for the home-screen app, so sign in once inside it with your passkey; it then stays signed in
+(`SESSION_DAYS`, default 180, renewed whenever you use it). Regenerate the artwork with `python3 tools/make-icons.py` (needs Pillow).
+
 ## Build and deploy with Gitea
 
 `.gitea/workflows/build.yml` builds the container on every push to `main` (and `v*` tags) and pushes it to