Fix subscription expiry logic and HTML entities in page titles

Subscription expiry (SubscriptionExpiryBackgroundService):
- Trials with no grace period now go directly Active -> Expired instead
  of briefly entering GracePeriod for a day, which was causing repeated
  'Grace Period Started' admin notification emails
- Remove redundant isTrial variable (query already filters to non-Stripe
  companies, so all processed companies are trials by definition)
- Save per-company inside the loop so a single SaveChangesAsync failure
  no longer discards all other companies' status changes and notification
  log entries (which was the other cause of repeated emails)

HTML entities in page titles (33 views):
- Replace – / — with plain ' - ' in ViewData["Title"] C#
  strings; Razor HTML-encodes these when rendering @ViewData["Title"],
  causing browsers to display the literal text '–' instead of a dash

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

src/PowderCoating.Web/Views/SubscriptionManagement/Manage.cshtml

@@ -2,7 +2,7 @@
 @using PowderCoating.Core.Enums
 @model Company
 @{
-    ViewData["Title"] = $"Manage – {Model.CompanyName}";
+    ViewData["Title"] = $"Manage - {Model.CompanyName}";
     var planConfigs = (dynamic)ViewBag.PlanConfigs;
 
     string PlanName(int plan)