feat: reminders, Excel customer import and security hardening

Features
- Payment reminders via Resend (candidates, send, history, test email)
- Bulk import of the customer list from Excel/CSV in the dashboard
- Dashboard i18n (en/nl) with language selector

Security
- Enforce venue isolation on all /venues/:venueId routes
- Require admin for planned-tab changes and pairing codes
- Rate-limit login and device registration; opt-in TRUST_PROXY
- Require JWT_SECRET in production; stop leaking internal errors
- Escape customer names in reminder emails

Sync and commands
- Remove tabs the terminal no longer reports; validate nested sync payload
- Return all pending commands on every sync (fixes missed-command race)
- First command ack wins; atomic registration code claim
- Reject commands for revoked devices, stale versions or duplicates
- Remind only unpaid balances, with a 7-day cooldown

Dashboard
- Share a single token refresh across concurrent 401s (random logouts)
- Keep the session alive for the refresh token lifetime

Deployment
- Replace `db push --accept-data-loss` with migrations (baselines legacy DBs)
- Set NODE_ENV=production; pass Resend and TRUST_PROXY env in prod compose

apps/dashboard/package.json

@@ -32,6 +32,7 @@
     "react-dom": "^18.2.0",
     "react-hook-form": "^7.49.0",
     "tailwind-merge": "^2.2.1",
+    "xlsx": "https://cdn.sheetjs.com/xlsx-0.20.3/xlsx-0.20.3.tgz",
     "zod": "^3.22.4"
   },
   "devDependencies": {