feat: Implement AI Gateway page with feature tiles and descriptions

feat: Update AppSidebar to include new Environments and Credentials sections

feat: Enhance node form with branch selection for triggers and deployment

feat: Create CredentialForm and CredentialRow components for managing credentials

feat: Add API endpoints for credential management

fix: Update node catalog defaults for deploy and promote nodes

web/app/gateway/page.tsx

@@ -1,10 +1,88 @@
-import { EmptySection } from "@/components/empty-section";
+"use client";
+
+import { Activity, ArrowLeftRight, Coins, Gauge, Radio } from "lucide-react";
+
+// Static preview of the AI Gateway concept. No real proxy yet — this
+// page is the contract we show clients while the gateway is being
+// built. When the runtime exists, replace the four feature tiles with
+// live config + metrics.
 
 export default function GatewayPage() {
   return (
-    <EmptySection
-      title="Gateway"
-      description="Public ingress for deployed agents — routes, auth, rate limits, OpenTelemetry export. Replaces the per-runtime gateway (Bedrock AgentCore endpoints, Vertex Reasoning Engine routes, K8s Ingress) with a uniform layer."
-    />
+    <div className="mx-auto w-full max-w-6xl space-y-6 p-6">
+      <div>
+        <div className="mb-1 flex items-center gap-2 text-[11px] font-medium uppercase tracking-wider text-muted-foreground">
+          <Radio className="size-3.5" />
+          Gateway
+        </div>
+        <h1 className="text-3xl font-semibold tracking-tight">AI Gateway</h1>
+        <p className="mt-1 max-w-3xl text-sm text-muted-foreground">
+          A proxy in front of your agents&rsquo; LLM calls. Enforce
+          per-agent budgets, log every prompt and completion for replay,
+          rate-limit by tenant, and fall back across providers without
+          redeploying.
+        </p>
+      </div>
+
+      <div className="rounded-lg border bg-card/40 p-5">
+        <div className="grid gap-4 md:grid-cols-2">
+          <FeatureTile
+            icon={Coins}
+            title="Budgets & cost caps"
+            body="Per-agent and per-environment spend ceilings. Hard cap or alert-only; the gateway short-circuits requests that would breach the budget."
+          />
+          <FeatureTile
+            icon={Activity}
+            title="Prompt + completion logs"
+            body="Every call captured for replay and incident review. Plumbs into the Operations pillar's trace store."
+          />
+          <FeatureTile
+            icon={Gauge}
+            title="Rate limits & quotas"
+            body="Throttle per tenant, per agent, or per route. Lives in the gateway, not the app — same policy across runtimes."
+          />
+          <FeatureTile
+            icon={ArrowLeftRight}
+            title="Provider fallback"
+            body="Try OpenAI → Anthropic → Bedrock on failure. Routing is config, not code, so swaps don't need a redeploy."
+          />
+        </div>
+
+        <div className="mt-6 flex items-center justify-end border-t pt-5">
+          <button
+            type="button"
+            disabled
+            className="rounded-md border bg-foreground/95 px-3 py-1.5 text-xs font-medium text-background opacity-90 disabled:cursor-not-allowed"
+            title="Coming soon"
+          >
+            + New gateway
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}
+
+function FeatureTile({
+  icon: Icon,
+  title,
+  body,
+}: {
+  icon: React.ComponentType<{ className?: string }>;
+  title: string;
+  body: string;
+}) {
+  return (
+    <div className="rounded-lg border bg-background/40 p-5">
+      <div className="flex items-start gap-3">
+        <div className="grid size-9 shrink-0 place-items-center rounded-md border bg-muted/30">
+          <Icon className="size-4 text-muted-foreground" />
+        </div>
+        <div className="min-w-0">
+          <div className="text-sm font-medium">{title}</div>
+          <p className="mt-1 text-xs text-muted-foreground">{body}</p>
+        </div>
+      </div>
+    </div>
   );
 }