feat(forms): make textarea monospace opt-in and improve multiline toggle

Add `monospace` prop to Textarea component so font-mono is no longer
applied by default. Apply it explicitly to env variable editors, private
key fields, and shared variable forms where monospace is appropriate.

Use Alpine.js x-data/x-model to make the multiline toggle reactive
without a full Livewire round-trip. Add wire:key on the input/textarea
wrappers to force proper DOM replacement when switching modes.

resources/css/app.css

@@ -15,6 +15,7 @@
 
 @theme {
     --font-sans: 'Geist Sans', Inter, sans-serif;
+    --font-mono: 'Geist Mono', 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;
     --font-geist-sans: 'Geist Sans', Inter, sans-serif;
     --font-logs: 'Geist Mono', 'SFMono-Regular', Consolas, 'Liberation Mono', Menlo, monospace;