fix(dashboard): show no-auth card for free providers instead of OAuth modal

OpenCode Free (noAuth: true) was routed through OAuthModal which tried to call
a non-existent /api/oauth/opencode/authorize endpoint, resulting in a 500 error.

Detect noAuth free providers via FREE_PROVIDERS[id]?.noAuth and render a
NoAuthProviderCard (lock_open + description) instead of the connections section
with the "+ Add" button that triggered the broken flow.

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

@@ -19,9 +19,11 @@ import {
   Toggle,
   Select,
   ProxyConfigModal,
+  NoAuthProviderCard,
 } from "@/shared/components";
 import {
   LOCAL_PROVIDERS,
+  FREE_PROVIDERS,
   getProviderAlias,
   isOpenAICompatibleProvider,
   isAnthropicCompatibleProvider,
@@ -1084,6 +1086,7 @@ export default function ProviderDetailPage() {
     providerInfo?.toggleAuthType === "oauth" || providerInfo?.toggleAuthType === "free";
   const providerSupportsPat = supportsApiKeyOnFreeProvider(providerId);
   const isOAuth = providerSupportsOAuth && !providerSupportsPat;
+  const isFreeNoAuth = FREE_PROVIDERS[providerId]?.noAuth === true;
   const registryModels = getModelsByProviderId(providerId);
   // Prefer synced API-discovered models when available, then merge built-ins
   // and user-managed custom models without duplicating IDs.
@@ -3167,7 +3170,8 @@ export default function ProviderDetailPage() {
       )}
 
       {/* Connections */}
-      {!isUpstreamProxyProvider && (
+      {!isUpstreamProxyProvider && isFreeNoAuth && <NoAuthProviderCard />}
+      {!isUpstreamProxyProvider && !isFreeNoAuth && (
         <Card>
           <div className="mb-4 flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
             <div className="flex min-w-0 flex-wrap items-center gap-2">

src/shared/components/NoAuthProviderCard.tsx

@@ -0,0 +1,21 @@
+"use client";
+
+import Card from "./Card";
+
+export default function NoAuthProviderCard() {
+  return (
+    <Card>
+      <div className="flex items-center gap-3">
+        <div className="inline-flex shrink-0 items-center justify-center w-10 h-10 rounded-full bg-green-500/10 text-green-500">
+          <span className="material-symbols-outlined text-[20px]">lock_open</span>
+        </div>
+        <div className="flex-1">
+          <p className="text-sm font-medium">No authentication required</p>
+          <p className="text-xs text-text-muted">
+            This provider is ready to use immediately — no signup or API key needed.
+          </p>
+        </div>
+      </div>
+    </Card>
+  );
+}

src/shared/components/index.tsx

@@ -32,6 +32,7 @@ export { default as NotificationToast } from "./NotificationToast";
 export { default as FilterBar } from "./FilterBar";
 export { default as ColumnToggle } from "./ColumnToggle";
 export { default as DataTable } from "./DataTable";
+export { default as NoAuthProviderCard } from "./NoAuthProviderCard";
 
 // Layouts
 export * from "./layouts";