Design consistency audit fixes: alerts, cards, dark mode, utilities

Alert sweep (113 alerts, 79 files):
  All persistent static banners now carry alert-permanent so the
  layout's 5-second auto-dismiss cannot swallow guidance, warnings,
  or validation errors. Transient dismissible toasts left untouched.

CSS fixes (site.css):
  .card.shadow-sm      — strips rogue border from ~40 drifted cards
  .card-header.bg-white — rebinds to var(--bs-body-bg) so card
                          headers follow dark/light theme correctly
  Typography utilities  — .text-2xs (.68rem), .text-xs (.73rem)
  Token color classes   — .text-ember, .text-ok, .text-bad,
                          .text-warn, .text-cool, .bg-paper-2
  Layout utilities      — .mw-xs/sm/md/lg replace inline max-width
  Comment              — documents text-ember vs text-primary intent

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

src/PowderCoating.Web/Views/PlatformSubscription/Edit.cshtml

@@ -1,4 +1,4 @@
-@using PowderCoating.Application.DTOs.Subscription
+@using PowderCoating.Application.DTOs.Subscription
 @model UpdateSubscriptionPlanConfigDto
 @{
     ViewData["Title"] = $"Edit {ViewBag.PlanName} Plan";
@@ -179,12 +179,12 @@
 
                     <h5 class="mb-3 pb-2 border-bottom mt-4">Stripe Integration</h5>
 
-                    <div class="alert alert-info small mb-3" role="alert">
+                    <div class="alert alert-info alert-permanent small mb-3" role="alert">
                         <i class="bi bi-info-circle me-2"></i>
                         <strong>Where to find price IDs:</strong>
                         In your <a href="https://dashboard.stripe.com/products" target="_blank" class="alert-link">Stripe Dashboard</a>,
                         open the product, then look in the <strong>Pricing</strong> section for the specific price.
-                        The ID starts with <code>price_</code> — <em>not</em> the product ID which starts with <code>prod_</code>.
+                        The ID starts with <code>price_</code> — <em>not</em> the product ID which starts with <code>prod_</code>.
                     </div>
 
                     <div class="row g-3 mb-4">