Fix hardware-pricing reveal so it respects the Tailwind grid layout

The wizard's EK / Kundenverkaufspreis fields live inside a
<div class="grid grid-cols-2 gap-md"> wrapper. Toggling its inline
display:block as the previous code did replaced the grid layout and
stacked the two inputs full-width. Switch the wrapper to start with
the Tailwind `hidden` utility and toggle `hidden`/`grid` on the
classList, so when hardware is filled in the two pricing fields
appear side by side. Functionality and the existing commission
formula (Provision + Aktionscodes − EK + VK, already covered by the
provisionService tests) are unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

public/index.html

@@ -1208,7 +1208,7 @@
                                        class="w-full bg-surface-container-lowest border border-outline-variant rounded-lg h-10 px-sm text-body-md text-on-surface focus:border-primary focus:ring-4 focus:ring-primary/20 outline-none">
                             </div>
 
-                            <div id="hardwarePricingFields" style="display:none;" class="grid grid-cols-2 gap-md">
+                            <div id="hardwarePricingFields" class="hidden grid-cols-2 gap-md">
                                 <div class="flex flex-col gap-base">
                                     <label class="text-label-caps text-on-surface-variant" for="hardwareEk">Hardware-EK</label>
                                     <input type="number" id="hardwareEk" name="hardware_ek" step="0.01" min="0" placeholder="0.00"