Phase G: Add Recurring Transactions (BackgroundService + CRUD UI)

- RecurringTemplate entity with Frequency/IntervalCount/NextFireDate/EndDate/MaxOccurrences/TemplateData JSON
- RecurringFrequency + RecurringTemplateType enums
- RecurringTransactionService BackgroundService: hourly check, creates Draft bills or immediate expenses, advances NextFireDate, auto-deactivates on limits
- RecurringTemplatesController: Index/Create/Edit/ToggleActive/Delete/GenerateNow (on-demand fire)
- Three views + external JS for type-toggle and dynamic bill line items
- Finance sidebar nav: Recurring Transactions
- Migration: AddRecurringTemplates

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

src/PowderCoating.Core/Enums/AccountingEnums.cs

@@ -94,6 +94,26 @@ public enum VendorCreditStatus
     Voided = 3
 }
 
+/// <summary>Source document type for a recurring template — controls which entity is created on each fire.</summary>
+public enum RecurringTemplateType
+{
+    /// <summary>Creates a vendor Bill (Draft, pending user review).</summary>
+    Bill = 1,
+    /// <summary>Creates a direct Expense entry (immediately recorded).</summary>
+    Expense = 2
+}
+
+/// <summary>How often a recurring template fires.</summary>
+public enum RecurringFrequency
+{
+    Daily = 1,
+    Weekly = 2,
+    BiWeekly = 3,
+    Monthly = 4,
+    Quarterly = 5,
+    Annually = 6
+}
+
 /// <summary>Lifecycle state of a Manual Journal Entry.</summary>
 public enum JournalEntryStatus
 {