Add Anthropic as a central integration

Lets the Claude API key be managed once in Portal → Settings →
Integrations and shared across apps (forecasting, wages), instead of
each app storing its own copy.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/integrations/schema.js

@@ -42,6 +42,11 @@ export const INTEGRATIONS = {
     configFields: ['site_url'],
     secretFields: [],
   },
+  anthropic: {
+    name: 'Anthropic (Claude)',
+    configFields: [],
+    secretFields: ['api_key'],
+  },
 }
 
 export const MASKED = '••••••••'