Org structure: divisions → products/services → teams + custom model base URL

The object spine becomes definable (data model was designed-for from day one):
- Division and Product entities (Product carries kind: Product|Service, optional DivisionId);
  Team gains nullable ProductId — pre-structure teams keep working. AddDivisionsAndProducts
  migration; org-scoped validation; owner-only writes (audited); list endpoints.
- /structure page: define divisions, products/services (with division), teams (under a
  product). Org chart now renders the full spine — org → divisions → products → teams →
  seats — with parentless layers linking up to the org.
- BYOK custom URL: the SeatsPage model-connection form gains a Base URL field (provider
  list: stub/openai/ollama/vllm/custom). Backend already supported it end to end —
  ApiConfig.Endpoint flows into the OpenAI-compatible adapter ({base}/v1/chat/completions),
  so any OpenAI-compatible gateway or self-hosted model works; the config list shows it.

Verified: ArchitectureTests 8/8, IntegrationTests 45/45 (new OrgStructureTests: spine
creation, kind tags, org-scoped validation 400s, Member 403), client build green.

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

client/src/App.tsx

@@ -9,6 +9,7 @@ import { OrgChartPage } from '@/pages/OrgChartPage'
 import { PerformancePage } from '@/pages/PerformancePage'
 import { ReviewsPage } from '@/pages/ReviewsPage'
 import { SeatsPage } from '@/pages/SeatsPage'
+import { StructurePage } from '@/pages/StructurePage'
 import { useAuth } from '@/store/auth'
 
 export default function App() {
@@ -25,6 +26,7 @@ export default function App() {
         <Route path="/cartable" element={token ? <CartablePage /> : <Navigate to="/login" replace />} />
         <Route path="/members" element={token ? <MembersPage /> : <Navigate to="/login" replace />} />
         <Route path="/org" element={token ? <OrgChartPage /> : <Navigate to="/login" replace />} />
+        <Route path="/structure" element={token ? <StructurePage /> : <Navigate to="/login" replace />} />
         <Route path="/performance" element={token ? <PerformancePage /> : <Navigate to="/login" replace />} />
         <Route path="*" element={<Navigate to="/" replace />} />
       </Routes>