fix: move orchestrate endpoints out of admin router

- Create backend/app/api/orchestrate.py — new router for workflow steps
  (scrape, generate, email, reminder, deadline, finalize) without admin auth.
- Remove orchestrate endpoints from backend/app/api/admin.py.
- Register orchestrate router in main.py under /api/orchestrate.
- Update frontend api/index.ts to call /orchestrate/{step} instead of
  /admin/orchestrate/{step}.

This lets family members trigger vote emails without an admin bearer token.

frontend/src/api/index.ts

@@ -64,7 +64,7 @@ export const mealPlannerApi = {
     getMealPlans: (params?: any) => api.get('/admin/meal-plans', { params }),
     getStats: () => api.get('/admin/stats'),
     testEmail: (email: string) => api.post('/admin/test-email', null, { params: { email } }),
-    triggerOrchestrate: (step: string, weekStart?: string) => api.post(`/admin/orchestrate/${step}`, null, { params: { week_start: weekStart } }),
+    triggerOrchestrate: (step: string, weekStart?: string) => api.post(`/orchestrate/${step}`, null, { params: { week_start: weekStart } }),
   },
 
   feedback: {