feat(org): panel-based access system replacing roles (procurement/inventory)

- new tables user_panels (panel: procurement/inventory/pm + level full/limited)
  and user_project_members (M:N membership, separate from pm responsibility)
- UserContext carries panels + member_project_ids; /users/me and the users
  list include them
- admin endpoints: PUT /users/{id}/panels, PUT /users/{id}/panel-projects
- inventory scope: panel inventory 'full' -> manager scope (all projects, NO
  stock change); 'limited' -> supervisor scope (own memberships, stock change
  allowed); legacy roles kept as migration fallback; admin untouched
- procurement writes: _procurement_writer is now panel-aware (admin, legacy
  procurement_manager, or procurement 'full') across all 18 write routers;
  quote CREATE additionally allows 'limited' users restricted to their member
  projects (validated server-side)
- frontend: panel-aware HomeRoute (inventory -> warehouse panel, procurement
  limited -> minimal RequesterHome), wizard project options restricted for
  limited users, change-inventory button/route gated to inventory 'limited',
  organization panel gains the panels & access-levels management section

backend/app/routers/auth.py

@@ -94,6 +94,6 @@ async def login(request: Request, payload: LoginRequest, db: AsyncSession = Depe
             "access_token": access_token,
             "token_type": "bearer",
             "expires_in": body.get("expires_in"),
-            "user": user_to_dict(ctx.user, projects),
+            "user": await user_to_dict(ctx.user, projects, db),
         }
     }