New app icon and login logo: the HamLab penguin

Every icon is rendered from web/scripts/logo-source.png by scripts/icons.mjs: trimmed to
the artwork's own edge, transparent corners for the browser icons, a dark ground from the
artwork's palette for iOS (which paints transparency black) and for Android's maskable
icon, where the whole artwork sits inside the 80% safe circle. The login screen no longer
crops the logo to a circle or repeats the wordmark. Service worker cache bumped so
installed apps fetch the new files.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

web/src/styles.css

@@ -16,7 +16,9 @@ button { font: inherit; color: inherit; background: none; border: 0; cursor: poi
 
 /* login */
 .login { display: flex; flex-direction: column; gap: 10px; width: min(320px, 90vw); }
-.login-logo { width: 160px; height: 160px; align-self: center; border-radius: 50%; margin-bottom: 4px; }
+/* the logo carries the wordmark now; the heading stays for screen readers and is not drawn twice */
+.login h1 { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
+.login-logo { width: 176px; height: 176px; align-self: center; margin-bottom: 4px; } /* the artwork brings its own shape: no circular crop */
 .login h1 { text-align: center;  margin: 0 0 8px; font-weight: 600; color: var(--accent); letter-spacing: .5px; }
 .login input { padding: 10px 12px; background: var(--bg2); border: 1px solid var(--border); border-radius: 6px; color: var(--fg); font-size: 16px; }
 .login button, .primary { padding: 10px 12px; background: var(--accent); color: var(--btn-fg); border-radius: 6px; font-weight: 600; }