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/Home/Error.cshtml

@@ -1,4 +1,4 @@
-@{
+@{
     ViewData["Title"] = "Error";
 }
 
@@ -20,7 +20,7 @@
 
                     @if (Context.TraceIdentifier != null)
                     {
-                        <div class="alert alert-secondary mt-3">
+                        <div class="alert alert-secondary alert-permanent mt-3">
                             <strong>Request ID:</strong> <code>@Context.TraceIdentifier</code>
                             <br />
                             <small class="text-muted">Please provide this ID when contacting support.</small>
@@ -56,7 +56,7 @@
             @if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development")
             {
                 var logFileName = $"logs/errors-{DateTime.Now:yyyyMMdd}.txt";
-                <div class="alert alert-warning mt-3">
+                <div class="alert alert-warning alert-permanent mt-3">
                     <strong><i class="bi bi-code-slash"></i> Development Mode:</strong>
                     Check the error logs at <code>@logFileName</code> for details.
                 </div>