feat(smzdm): require 1:1 cover and surface image fetch failure prompt

Add SMZDM to the cover-required platform list on both client and server,
register a 800x800 native cover spec in the admin cover catalog, and
normalize the desktop-client `smzdm_image_fetch_failed` adapter error to a
user-friendly Chinese prompt across the publisher error pipeline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/lib/cover-requirements.ts

@@ -51,6 +51,15 @@ const requirementCatalog: Record<string, Partial<PlatformCoverRequirement>> = {
     outputHeight: 900,
     priority: 90,
   },
+  smzdm: {
+    required: true,
+    supportMode: 'native',
+    aspectRatio: 1,
+    aspectLabel: '1:1',
+    outputWidth: 800,
+    outputHeight: 800,
+    priority: 90,
+  },
 }
 
 export function getPlatformCoverRequirements(