v0.1.21 - Mix calculator composer restyle

Mirror the throughput composer's green design language on the mix calculator
inputs: brand-tinted composer surface with a calculator-icon header, green
48px fields, Mix Name disabled until a client is chosen, a darker readable
on-brand hint, and optional notes via the "+ Add a note" reveal.

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

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "hunter-app",
-  "version": "0.1.20",
+  "version": "0.1.21",
   "private": true,
   "type": "module",
   "scripts": {