[FEAT] Fase 2 backend: campagne questionario (questionnaire_campaigns) + scadenze/ricorrenze

- createCampaign(supplierId): invia un template a un fornitore via questionnaire_campaigns
  (token sq_ retrocompat, scadenza/ricorrenza/reminder_offsets configurabili, crea
  supplier_user per accesso OTP, email invito col link al portale). Migrazioni 034+035
  applicate su host.
- campaigns(): cruscotto con semaforo scadenze (success/warning<=7gg/danger scaduto)
  + answers_count per campagna.
- computeNextReminder(): helper per il prossimo reminder dagli offset.
- Route: GET:campaigns, POST:{id}/campaigns. api.js: getQuestionnaireCampaigns,
  createQuestionnaireCampaign.

Smoke: rotte 401 (router+auth ok). php -l + node --check OK. USR2 applicato.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/index.php

@@ -293,6 +293,9 @@ $actionMap = [
         'PUT:questions/{subId}'          => 'updateTemplateQuestion',
         'DELETE:questions/{subId}'       => 'deleteTemplateQuestion',
         'POST:import'                    => 'importSuppliers',
+        // Campagne questionario (Fase 2): cruscotto + invio template a fornitore
+        'GET:campaigns'                  => 'campaigns',
+        'POST:{id}/campaigns'            => 'createCampaign',   // {id} = supplier id
         'GET:{id}'                  => 'get',
         'PUT:{id}'                  => 'update',
         'DELETE:{id}'               => 'delete',