fix(vendor): stop detail route crashing when vendor fetch fails

The vendor detail page and layout called api.vendors.getById without a
try/catch. The API client throws ApiError on any non-2xx, so a 404 (missing
vendor), 401, or 5xx during SSR threw out of the server component and
white-screened the whole route with a generic "server-side exception" —
the existing `if (!vendor)` fallback was never reached.

Guard both fetches: log the error and degrade gracefully (page shows
"Vendor not found", layout renders chrome with a fallback title).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/dashboard/app/(authenticated)/purchase/vendor/[id]/layout.tsx

@@ -10,8 +10,15 @@ export default async function layout(props: {
 }) {
     const { id } = await props.params
     const api = await getServerApi()
+    // Guard the fetch: a failed request (404/401/5xx) must not throw and crash
+    // the whole route — render the chrome with a fallback title instead.
+    let vendor: Record<string, any> | undefined
+    try {
         const response = (await api.vendors.getById(id)) as { data?: Record<string, any> }
-    const vendor = response?.data
+        vendor = response?.data
+    } catch (err) {
+        console.error(`Failed to load vendor ${id} (layout):`, err)
+    }
 
     const company = vendor?.company_name as string | undefined
     const fullName = [vendor?.first_name, vendor?.last_name].filter(Boolean).join(" ").trim()

apps/dashboard/app/(authenticated)/purchase/vendor/[id]/page.tsx

@@ -6,8 +6,15 @@ export default async function VendorDetailPage(props: { params: Promise<{ id: st
     const api = await getServerApi()
     // The OpenAPI schema doesn't yet describe GET /api/vendors/{id} (only PUT/DELETE),
     // so cast through `any` here until the schema is regenerated.
+    // Guard the fetch: a failed request (404/401/5xx) must degrade gracefully
+    // instead of throwing and white-screening the whole route.
+    let vendor: Record<string, any> | undefined
+    try {
         const response = (await api.vendors.getById(id)) as { data?: Record<string, any> }
-    const vendor = response?.data
+        vendor = response?.data
+    } catch (err) {
+        console.error(`Failed to load vendor ${id}:`, err)
+    }
 
     if (!vendor) {
         return <div className="text-muted-foreground p-6">Vendor not found.</div>