docs: split Structure into six linked department pages

sidebars/organization.ts

@@ -1,2 +1,7 @@
 import type {SidebarsConfig} from '@docusaurus/plugin-content-docs';
-export default {organizationSidebar: ['structure', 'collaboration', 'sdlc']} satisfies SidebarsConfig;
+export default {organizationSidebar: [
+  {type: 'category', label: 'Structure', link: {type: 'doc', id: 'structure'},
+    items: ['structure/product', 'structure/technology', 'structure/operations',
+      'structure/marketing', 'structure/finance-accounting', 'structure/hr-administration']},
+  'collaboration', 'sdlc',
+]} satisfies SidebarsConfig;