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/api/src/devices/dto/sync.dto.ts

@@ -1,9 +1,11 @@
-import { IsString, IsOptional, IsArray, IsInt, Min, IsUUID } from 'class-validator';
+import { IsString, IsOptional, IsArray, IsInt, Min, IsUUID, ValidateNested, ArrayMaxSize, IsNotEmpty } from 'class-validator';
+import { Type } from 'class-transformer';
 import { ApiProperty, ApiPropertyOptional } from '@nestjs/swagger';
 
 class OpenTabDto {
   @ApiProperty({ example: 'local-tab-uuid' })
   @IsString()
+  @IsNotEmpty()
   id: string;
 
   @ApiProperty({ example: 'Jan' })
@@ -38,5 +40,8 @@ export class SyncDto {
 
   @ApiProperty({ type: [OpenTabDto] })
   @IsArray()
+  @ArrayMaxSize(1000)
+  @ValidateNested({ each: true })
+  @Type(() => OpenTabDto)
   openTabs: OpenTabDto[];
 }