Add manual invoice creation mode with new API & UI flow

Introduced "ModeB" for manual invoice creation in system config. Added backend endpoints and service logic for creating invoices from confirmed Shop POs, with validation and error handling. Updated DTOs to support optional CreatedByUserId. On the frontend, added configuration card to toggle modes, a dialog for manual invoice creation, and UI updates to support the new workflow. Enables admins to choose between automatic and manual invoice creation.

distribution_fe/app/(dashboard)/configuration/page.tsx

@@ -2,6 +2,7 @@
 
 import { ProductCapabilitiesCard } from './_components/product-capabilities-card'
 import { GrnTaxCard } from './_components/grn-tax-card'
+import { InvoiceCreationModeCard } from './_components/invoice-creation-mode-card'
 
 export default function ConfigurationPage() {
   return (
@@ -11,7 +12,6 @@ export default function ConfigurationPage() {
         <p className="text-sm text-muted-foreground mt-0.5">System-wide settings, grouped by area</p>
       </div>
 
-      {/* 12-column grid: each card takes 6 columns so the two sit side by side; they stack on narrow screens. */}
       <div className="grid grid-cols-12 items-stretch gap-6">
         <div className="col-span-12 flex lg:col-span-6 [&>*]:w-full">
           <ProductCapabilitiesCard />
@@ -19,6 +19,9 @@ export default function ConfigurationPage() {
         <div className="col-span-12 flex lg:col-span-6 [&>*]:w-full">
           <GrnTaxCard />
         </div>
+        <div className="col-span-12 flex lg:col-span-6 [&>*]:w-full">
+          <InvoiceCreationModeCard />
+        </div>
       </div>
     </div>
   )