feat: add 14 new smart folder categories (locale-agnostic)

New EmailCategory enum values: Travel, Subscriptions, Parcels,
Recruitment, Events, SecurityAlerts, Healthcare, Education,
NewsMedia, PropertyUtilities, Charity, Government, CryptoInvesting,
FamilySchool.

HeuristicClassifier: locale-agnostic rules using global brand
domains + TLD patterns (.gov.*, .edu, .ac.*) + English subject
keywords — works for international users without relying on
country-specific domains (e.g. gov.uk).

Priority order ensures SecurityAlerts and Government take
precedence over Finance, and Travel/RideSharing/FoodDelivery
fire before Finance to prevent receipt mis-classification.

AnalyticsService: maps all 14 new slugs to category counts.
client.js: folderToRequest() handles all 14 new slugs.
Layout.jsx: SMART_FOLDERS extended with icons and labels.
widgets.jsx: CAT_SLUG updated for dashboard drillthrough.

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

src/InboxIntel.Domain/Enums/Enums.cs

@@ -16,7 +16,21 @@ public enum EmailCategory
     FoodDelivery = 10,
     SeasonalSales = 11,
     Wellness = 12,
-    Shopping = 13
+    Shopping = 13,
+    Travel = 14,
+    Subscriptions = 15,
+    Parcels = 16,
+    Recruitment = 17,
+    Events = 18,
+    SecurityAlerts = 19,
+    Healthcare = 20,
+    Education = 21,
+    NewsMedia = 22,
+    PropertyUtilities = 23,
+    Charity = 24,
+    Government = 25,
+    CryptoInvesting = 26,
+    FamilySchool = 27
 }
 
 /// <summary>State machine for a sync run.</summary>