New PWA icons: slate/blue weather icon, distinct dashboard icon, safe-zone maskable

- Redrawn sun-and-cloud icon in the current palette; artwork sits inside the maskable safe zone
  (the old one was clipped by round/squircle masks and used the old warm colours)
- Separate 'any' and 'maskable' manifest entries; opaque iOS touch icons
- Station Dashboard gets its own chart icon so both installed apps are distinguishable
- Vector favicon + PNG fallback; icons verified served by both manifests

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

app/public/index.html

@@ -6,6 +6,8 @@
 <link rel="stylesheet" href="/pwa-safe.css">
 <title>NeCloud Weather</title>
 <link rel="manifest" href="/manifest.json">
+<link rel="icon" type="image/svg+xml" href="/icons/icon.svg">
+<link rel="icon" type="image/png" sizes="192x192" href="/icons/icon-192.png">
 <link rel="apple-touch-icon" href="/icons/apple-touch-icon.png">
 <meta name="theme-color" content="#edf2f7" media="(prefers-color-scheme: light)">
 <meta name="theme-color" content="#070c14" media="(prefers-color-scheme: dark)">