feat(providers/codex): bulk add accounts via JSON

Add a "Bulk Add" button on /dashboard/providers/codex that imports
multiple OAuth accounts at once by pasting a JSON array, single object,
or { accounts: [...] } wrapper.

- New endpoint POST /api/oauth/codex/bulk-import (serial loop, no token echo)
- New BulkImportCodexModal component with JSON textarea + success/failure summary
- Persist idToken/lastRefreshAt on first insert via OPTIONAL_FIELDS
- Backfill email/chatgptAccountId/chatgptPlanType from JWT when missing
- Derive expiresAt from expiresIn when missing
- Gated to providerId === "codex" only; other providers unaffected

Co-authored-by: Cursor <cursoragent@cursor.com>

src/app/(dashboard)/dashboard/providers/[id]/page.js

@@ -17,6 +17,7 @@ import ConnectionRow from "./ConnectionRow";
 import AddApiKeyModal from "./AddApiKeyModal";
 import EditCompatibleNodeModal from "./EditCompatibleNodeModal";
 import AddCustomModelModal from "./AddCustomModelModal";
+import BulkImportCodexModal from "./BulkImportCodexModal";
 
 const ONE_BY_ONE_DELAY_MS = 1000;
 
@@ -36,6 +37,7 @@ export default function ProviderDetailPage() {
   const [showIFlowCookieModal, setShowIFlowCookieModal] = useState(false);
   const [showAddApiKeyModal, setShowAddApiKeyModal] = useState(false);
   const [addConnectionError, setAddConnectionError] = useState("");
+  const [showBulkImportCodex, setShowBulkImportCodex] = useState(false);
   const [showEditModal, setShowEditModal] = useState(false);
   const [showEditNodeModal, setShowEditNodeModal] = useState(false);
   const [showBulkProxyModal, setShowBulkProxyModal] = useState(false);
@@ -1339,6 +1341,11 @@ export default function ProviderDetailPage() {
                         Cookie
                       </Button>
                     )}
+                    {providerId === "codex" && (
+                      <Button size="sm" icon="playlist_add" variant="secondary" onClick={() => setShowBulkImportCodex(true)}>
+                        {translate("Bulk Add")}
+                      </Button>
+                    )}
                     <Button
                       size="sm"
                       icon="add"
@@ -1383,6 +1390,18 @@ export default function ProviderDetailPage() {
                       Cookie
                     </Button>
                   )}
+                  {providerId === "codex" && (
+                    <Button
+                      size="sm"
+                      icon="playlist_add"
+                      variant="secondary"
+                      onClick={() => setShowBulkImportCodex(true)}
+                      title={translate("Bulk import codex accounts from JSON")}
+                      className="w-full sm:w-auto"
+                    >
+                      {translate("Bulk Add")}
+                    </Button>
+                  )}
                   {hasDualAuthModes ? (
                     <>
                       <Button
@@ -1544,6 +1563,14 @@ export default function ProviderDetailPage() {
         />
       )}
 
+      {providerId === "codex" && (
+        <BulkImportCodexModal
+          isOpen={showBulkImportCodex}
+          onClose={() => setShowBulkImportCodex(false)}
+          onSuccess={fetchConnections}
+        />
+      )}
+
       {/* AG Risk Confirmation Modal */}
       <ConfirmModal
         isOpen={showAgRiskModal}