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

.idea/.gitignore

@@ -0,0 +1,10 @@
+# Default ignored files
+/shelf/
+/workspace.xml
+# Editor-based HTTP Client requests
+/httpRequests/
+# Ignored default folder with query files
+/queries/
+# Datasource local storage ignored files
+/dataSources/
+/dataSources.local.xml