File Search: quotas, licence gate and pause notifications #1386

Part of #1379.

Hard quotas per plan (Cloud: trial and Starter 1 connector / 500 files, Team 3 / 2,000, daily sync; Enterprise by contract down to 15 min. Self-hosted: Starter 500, Team 2,000, Enterprise unlimited down to 5 min; Community only during the 30-day trial). EditionService.assertPaidOrTrial, usage rows on the licence page, 80 % warning, pause e-mails, licence-pause retention (30 days), checkout sources file_quota_setup, file_quota, file_search_licence.