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>

public/style.css

@@ -240,3 +240,9 @@ textarea { padding: 12px 14px; resize: vertical; font-family: inherit; }
 .donetask .tick { color: var(--accent); }
 .donetask .tick circle { fill: var(--accent); stroke: var(--accent); }
 .donetask .tick path { stroke: var(--accent-t); }
+
+/* iOS home-screen app polish */
+html { -webkit-text-size-adjust: 100%; overscroll-behavior: none; }
+body { -webkit-touch-callout: none; }
+button, a, .row { -webkit-user-select: none; user-select: none; }
+input, textarea, [contenteditable], .sheet p, .card p, #view .sub { -webkit-user-select: text; user-select: text; }