revert: Remove accordion grouping + add AlertDialog

1. Reverted Accordion Grouping ✅
   Problem: Payment titles are editable by users
   - User renames "BNI Virtual Account" to "BNI VA 2"
   - Grouping breaks - gateway moves to new accordion
   - Confusing UX when titles change

   Solution: Back to flat list
   - All payment methods in one list
   - Titles can be edited without breaking layout
   - Simpler, more predictable behavior

2. Added AlertDialog Component ✅
   Installed: @radix-ui/react-alert-dialog
   Created: alert-dialog.tsx (shadcn pattern)

   Use for confirmations:
   - "Are you sure you want to delete?"
   - "Discard unsaved changes?"
   - "Disable payment method?"

   Example:
   <AlertDialog>
     <AlertDialogTrigger>Delete</AlertDialogTrigger>
     <AlertDialogContent>
       <AlertDialogHeader>
         <AlertDialogTitle>Are you sure?</AlertDialogTitle>
         <AlertDialogDescription>
           This action cannot be undone.
         </AlertDialogDescription>
       </AlertDialogHeader>
       <AlertDialogFooter>
         <AlertDialogCancel>Cancel</AlertDialogCancel>
         <AlertDialogAction>Delete</AlertDialogAction>
       </AlertDialogFooter>
     </AlertDialogContent>
   </AlertDialog>

Shadcn Dialog Components:
✅ Dialog - Forms, settings (@radix-ui/react-dialog)
✅ Drawer - Mobile bottom sheet (vaul)
✅ AlertDialog - Confirmations (@radix-ui/react-alert-dialog)

All three are official shadcn components!

admin-spa/package-lock.json

@@ -9,6 +9,7 @@
             "version": "0.0.1",
             "dependencies": {
                 "@radix-ui/react-accordion": "^1.2.12",
+                "@radix-ui/react-alert-dialog": "^1.1.15",
                 "@radix-ui/react-avatar": "^1.1.10",
                 "@radix-ui/react-checkbox": "^1.3.3",
                 "@radix-ui/react-dialog": "^1.1.15",
@@ -1191,6 +1192,34 @@
                 }
             }
         },
+        "node_modules/@radix-ui/react-alert-dialog": {
+            "version": "1.1.15",
+            "resolved": "https://registry.npmjs.org/@radix-ui/react-alert-dialog/-/react-alert-dialog-1.1.15.tgz",
+            "integrity": "sha512-oTVLkEw5GpdRe29BqJ0LSDFWI3qu0vR1M0mUkOQWDIUnY/QIkLpgDMWuKxP94c2NAC2LGcgVhG1ImF3jkZ5wXw==",
+            "license": "MIT",
+            "dependencies": {
+                "@radix-ui/primitive": "1.1.3",
+                "@radix-ui/react-compose-refs": "1.1.2",
+                "@radix-ui/react-context": "1.1.2",
+                "@radix-ui/react-dialog": "1.1.15",
+                "@radix-ui/react-primitive": "2.1.3",
+                "@radix-ui/react-slot": "1.2.3"
+            },
+            "peerDependencies": {
+                "@types/react": "*",
+                "@types/react-dom": "*",
+                "react": "^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc",
+                "react-dom": "^16.8 || ^17.0 || ^18.0 || ^19.0 || ^19.0.0-rc"
+            },
+            "peerDependenciesMeta": {
+                "@types/react": {
+                    "optional": true
+                },
+                "@types/react-dom": {
+                    "optional": true
+                }
+            }
+        },
         "node_modules/@radix-ui/react-arrow": {
             "version": "1.1.7",
             "resolved": "https://registry.npmjs.org/@radix-ui/react-arrow/-/react-arrow-1.1.7.tgz",