v0.1.20 - Even composer fields on laptops & add-success modal

- Throughput: even three-across layout for the "Add a packing run" fields
  on laptop widths so placeholders stay readable in the narrow content band
- Throughput: centred "Added" confirmation modal with in-card confetti on
  save (3s), composer clears for the next entry
- Fix stray character in changelog.ts type comment

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "hunter-app",
-  "version": "0.1.19",
+  "version": "0.1.20",
   "private": true,
   "type": "module",
   "scripts": {