Add PWA support and expandable draw canvas

PWA:
- manifest.json with name, icons, theme/background color, standalone display
- PNG icons (192, 512, 180 apple-touch) generated via pure Node.js (no deps)
- index.html: manifest link, theme-color, apple-mobile-web-app-* meta tags,
  viewport-fit=cover for iPhone notch/Dynamic Island
- service worker extended to cache app shell (static assets + index.html)
  with network-first for navigation, cache-first for hashed assets,
  network-first-with-cache-fallback for external Bible APIs

Expandable canvas:
- "Add More Space" button below each draw canvas adds a full notebook page
- Existing ink rescales to preserve visual pixel positions (no stretching)
- Page count embedded as metadata in the strokes array so it survives
  navigation without a separate state key

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/manifest.json

@@ -0,0 +1,25 @@
+{
+  "name": "Bible Study Project",
+  "short_name": "Bible Study",
+  "description": "Your personal verse-by-verse Bible study companion",
+  "start_url": "/",
+  "scope": "/",
+  "display": "standalone",
+  "orientation": "any",
+  "background_color": "#f8fafc",
+  "theme_color": "#0f172a",
+  "icons": [
+    {
+      "src": "/icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}