Auto create initial monthly engagement from subscription

app/modules/services/subscriptions_ui.py

@@ -514,6 +514,35 @@ def subscription_bulk_submit(
         if plan_effective_from and plan_effective_to and plan_effective_to < plan_effective_from:
             return RedirectResponse("/services/subscriptions/bulk?error=period", 303)
 
+        if (
+            generation_mode == "subscription_only"
+            and auto_generate_periods is not None
+            and recurrence_type == "monthly"
+            and plan_effective_from is not None
+        ):
+            if plan_effective_from.month == 1:
+                initial_monthly_period = f"{plan_effective_from.year - 1:04d}-12"
+            else:
+                initial_monthly_period = (
+                    f"{plan_effective_from.year:04d}-{plan_effective_from.month - 1:02d}"
+                )
+            try:
+                requested_periods = [normalize_period_label(
+                    initial_monthly_period,
+                    financial_year=selected_financial_year,
+                    recurrence_type=recurrence_type,
+                )]
+            except ValueError:
+                return RedirectResponse("/services/subscriptions/bulk?error=period", 303)
+
+            locked = redirect_if_financial_year_locked(
+                db,
+                tenant_id=tenant_id,
+                year_code=selected_financial_year,
+                redirect_url="/services/subscriptions/bulk?error=financial_year",
+            )
+            if locked:
+                return locked
         for token in selected_tokens:
             try:
                 client, scope_type, scope_key, business_unit_id, client_branch_id, registration_id = resolve_scope_target(