feat: Etiketten-Seitenlayout auf dem A4-Bogen frei waehlbar

- LabelTemplate bekommt columns/rows (optional, leer = automatisch
  passend), plus konfigurierbare Raender/Abstaende - damit ein Etikett
  exakt auf das vorgedruckte Raster eines physischen Etikettenbogens
  (z.B. Avery) gelegt werden kann statt nur automatisch berechnet
- Startposition beim Drucken waehlbar, fuer bereits angebrochene Boegen
  (erste Seite startet ab der gewaehlten Position, Folgeseiten wieder
  von vorne)

ApiCore-Backend/prisma/migrations/20260901173228_label_template_sheet_layout/migration.sql

@@ -0,0 +1,9 @@
+-- Explicit A4 sheet layout per LabelTemplate: columns/rows (nullable, null =
+-- auto-fit) plus configurable page margins and gaps, so a template can be
+-- made to match a specific physical label sheet's exact printed grid.
+ALTER TABLE "LabelTemplate" ADD COLUMN "columns" INTEGER;
+ALTER TABLE "LabelTemplate" ADD COLUMN "rows" INTEGER;
+ALTER TABLE "LabelTemplate" ADD COLUMN "marginTopMm" DOUBLE PRECISION NOT NULL DEFAULT 5;
+ALTER TABLE "LabelTemplate" ADD COLUMN "marginLeftMm" DOUBLE PRECISION NOT NULL DEFAULT 5;
+ALTER TABLE "LabelTemplate" ADD COLUMN "gapXMm" DOUBLE PRECISION NOT NULL DEFAULT 2;
+ALTER TABLE "LabelTemplate" ADD COLUMN "gapYMm" DOUBLE PRECISION NOT NULL DEFAULT 2;

ApiCore-Backend/prisma/schema.prisma

@@ -864,6 +864,17 @@ model LabelTemplate {
   elements  Json     @default("[]")
   widthMm   Float    @default(90)
   heightMm  Float    @default(35)
+  // A4 sheet layout. columns/rows are nullable: null means "auto-fit as many
+  // as fit" (the original behaviour); a real label sheet product (e.g. a
+  // specific Avery SKU) publishes an exact columns/rows/margin/gap grid, so
+  // setting these lets a template's printed positions match the physical,
+  // pre-die-cut sheet instead of just whatever the naive fit computes.
+  columns      Int?
+  rows         Int?
+  marginTopMm  Float @default(5)
+  marginLeftMm Float @default(5)
+  gapXMm       Float @default(2)
+  gapYMm       Float @default(2)
   isDefault Boolean  @default(false)
   active    Boolean  @default(true)
   createdAt DateTime @default(now())

ApiCore-Backend/src/label-templates/dto/create-label-template.dto.ts

@@ -4,6 +4,7 @@ import {
   ArrayMaxSize,
   IsArray,
   IsBoolean,
+  IsInt,
   IsNumber,
   IsOptional,
   IsString,
@@ -36,6 +37,47 @@ export class CreateLabelTemplateDto {
   @Min(10)
   heightMm?: number;
 
+  @ApiPropertyOptional({
+    description:
+      'Spalten pro A4-Bogen. Leer = automatisch so viele wie passen.',
+  })
+  @IsOptional()
+  @IsInt()
+  @Min(1)
+  columns?: number;
+
+  @ApiPropertyOptional({
+    description: 'Zeilen pro A4-Bogen. Leer = automatisch so viele wie passen.',
+  })
+  @IsOptional()
+  @IsInt()
+  @Min(1)
+  rows?: number;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  marginTopMm?: number;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  marginLeftMm?: number;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  gapXMm?: number;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsNumber()
+  @Min(0)
+  gapYMm?: number;
+
   @ApiPropertyOptional()
   @IsOptional()
   @IsBoolean()

ApiCore-Backend/src/label-templates/label-templates.controller.ts

@@ -4,8 +4,10 @@ import {
   Delete,
   Get,
   Param,
+  ParseIntPipe,
   Patch,
   Post,
+  Query,
   Res,
 } from '@nestjs/common';
 import { ApiBearerAuth, ApiTags } from '@nestjs/swagger';
@@ -65,11 +67,14 @@ export class LabelTemplatesController {
   async print(
     @Param('id') id: string,
     @Param('bottlingBatchId') bottlingBatchId: string,
+    @Query('startPosition', new ParseIntPipe({ optional: true }))
+    startPosition: number | undefined,
     @Res() res: Response,
   ): Promise<void> {
     const pdf = await this.labelTemplatesService.renderLabelsPdf(
       id,
       bottlingBatchId,
+      startPosition,
     );
     res.setHeader('Content-Type', 'application/pdf');
     res.setHeader(

ApiCore-Backend/src/label-templates/label-templates.service.spec.ts

@@ -64,6 +64,12 @@ describe('LabelTemplatesService', () => {
     elements,
     widthMm: 90,
     heightMm: 35,
+    columns: null,
+    rows: null,
+    marginTopMm: 5,
+    marginLeftMm: 5,
+    gapXMm: 2,
+    gapYMm: 2,
     isDefault: false,
     active: true,
   };
@@ -213,5 +219,56 @@ describe('LabelTemplatesService', () => {
       // A PDF with an embedded raster image contains an XObject /Image entry.
       expect(pdf.toString('latin1')).toContain('/Image');
     });
+
+    function countPages(pdf: Buffer): number {
+      const matches = pdf.toString('latin1').match(/\/Type\s*\/Page[^s]/g);
+      return matches ? matches.length : 0;
+    }
+
+    it('uses an explicit columns/rows override instead of auto-fitting', async () => {
+      prisma.labelTemplate.findUnique.mockResolvedValue({
+        ...template,
+        columns: 1,
+        rows: 1,
+      });
+      prisma.bottlingBatch.findUnique.mockResolvedValue({
+        id: 'batch-1',
+        jarSize: 500,
+        jarCount: 3,
+        lotNumber: 'L-001',
+        date: new Date('2026-06-01T00:00:00.000Z'),
+        bestBeforeDate: new Date('2028-06-01T00:00:00.000Z'),
+        honeyBatch: { batchNumber: 'HB-001', honeyType: 'Bluetenhonig' },
+        product: { name: 'Glas 500g' },
+      });
+
+      const pdf = await service.renderLabelsPdf('template-1', 'batch-1');
+
+      expect(countPages(pdf)).toBe(3);
+    });
+
+    it('skips already-used slots on the first sheet via startPosition, but not later sheets', async () => {
+      prisma.labelTemplate.findUnique.mockResolvedValue({
+        ...template,
+        columns: 2,
+        rows: 1,
+      });
+      prisma.bottlingBatch.findUnique.mockResolvedValue({
+        id: 'batch-1',
+        jarSize: 500,
+        jarCount: 3,
+        lotNumber: 'L-001',
+        date: new Date('2026-06-01T00:00:00.000Z'),
+        bestBeforeDate: new Date('2028-06-01T00:00:00.000Z'),
+        honeyBatch: { batchNumber: 'HB-001', honeyType: 'Bluetenhonig' },
+        product: { name: 'Glas 500g' },
+      });
+
+      const pdf = await service.renderLabelsPdf('template-1', 'batch-1', 2);
+
+      // perPage=2, skip=1: label 1 fills the remaining slot on page 1,
+      // labels 2-3 fill both slots of page 2.
+      expect(countPages(pdf)).toBe(2);
+    });
   });
 });

ApiCore-Backend/src/label-templates/label-templates.service.ts

@@ -13,12 +13,21 @@ import {
 } from './label-element.types';
 
 const MM_TO_PT = 72 / 25.4;
-const PAGE_MARGIN_MM = 5;
-const LABEL_GAP_MM = 2;
 const A4_WIDTH_MM = 210;
 const A4_HEIGHT_MM = 297;
 const QR_SOURCE_SIZE_PX = 400;
 
+interface SheetLayout {
+  widthMm: number;
+  heightMm: number;
+  columns: number | null;
+  rows: number | null;
+  marginTopMm: number;
+  marginLeftMm: number;
+  gapXMm: number;
+  gapYMm: number;
+}
+
 function formatDate(date: Date): string {
   return date.toLocaleDateString('de-DE');
 }
@@ -151,6 +160,7 @@ export class LabelTemplatesService {
   async renderLabelsPdf(
     templateId: string,
     bottlingBatchId: string,
+    startPosition = 1,
   ): Promise<Buffer> {
     const template = await this.findById(templateId);
     const bottlingBatch = await this.prisma.bottlingBatch.findUnique({
@@ -193,19 +203,28 @@ export class LabelTemplatesService {
 
     return this.renderPdf(
       elements,
-      template.widthMm,
-      template.heightMm,
+      {
+        widthMm: template.widthMm,
+        heightMm: template.heightMm,
+        columns: template.columns,
+        rows: template.rows,
+        marginTopMm: template.marginTopMm,
+        marginLeftMm: template.marginLeftMm,
+        gapXMm: template.gapXMm,
+        gapYMm: template.gapYMm,
+      },
       bottlingBatch.jarCount,
       qrCodeBuffer,
+      startPosition,
     );
   }
 
   private renderPdf(
     elements: LabelElement[],
-    widthMm: number,
-    heightMm: number,
+    layout: SheetLayout,
     copies: number,
     qrCodeBuffer: Buffer | null,
+    startPosition: number,
   ): Promise<Buffer> {
     return new Promise((resolve, reject) => {
       const doc = new PDFDocument({ size: 'A4', margin: 0 });
@@ -214,27 +233,34 @@ export class LabelTemplatesService {
       doc.on('end', () => resolve(Buffer.concat(chunks)));
       doc.on('error', (error: Error) => reject(error));
 
-      const usableWidthMm = A4_WIDTH_MM - 2 * PAGE_MARGIN_MM;
-      const usableHeightMm = A4_HEIGHT_MM - 2 * PAGE_MARGIN_MM;
-      const columns = Math.max(
-        1,
-        Math.floor((usableWidthMm + LABEL_GAP_MM) / (widthMm + LABEL_GAP_MM)),
-      );
-      const rows = Math.max(
-        1,
-        Math.floor((usableHeightMm + LABEL_GAP_MM) / (heightMm + LABEL_GAP_MM)),
-      );
+      const { widthMm, heightMm, marginTopMm, marginLeftMm, gapXMm, gapYMm } =
+        layout;
+      const usableWidthMm = A4_WIDTH_MM - 2 * marginLeftMm;
+      const usableHeightMm = A4_HEIGHT_MM - 2 * marginTopMm;
+      const columns =
+        layout.columns ??
+        Math.max(1, Math.floor((usableWidthMm + gapXMm) / (widthMm + gapXMm)));
+      const rows =
+        layout.rows ??
+        Math.max(
+          1,
+          Math.floor((usableHeightMm + gapYMm) / (heightMm + gapYMm)),
+        );
       const perPage = columns * rows;
+      // startPosition only skips ahead on the first sheet (partially-used
+      // physical sheet, e.g. a few labels already peeled off) - every sheet
+      // after that always starts fresh at the top-left slot.
+      const skip = Math.min(Math.max(0, startPosition - 1), perPage - 1);
 
       for (let index = 0; index < copies; index += 1) {
-        const onPage = index % perPage;
-        if (index > 0 && onPage === 0) {
+        const slotOnPage = (skip + index) % perPage;
+        if (index > 0 && slotOnPage === 0) {
           doc.addPage({ size: 'A4', margin: 0 });
         }
-        const column = onPage % columns;
-        const row = Math.floor(onPage / columns);
-        const xMm = PAGE_MARGIN_MM + column * (widthMm + LABEL_GAP_MM);
-        const yMm = PAGE_MARGIN_MM + row * (heightMm + LABEL_GAP_MM);
+        const column = slotOnPage % columns;
+        const row = Math.floor(slotOnPage / columns);
+        const xMm = marginLeftMm + column * (widthMm + gapXMm);
+        const yMm = marginTopMm + row * (heightMm + gapYMm);
         const originX = xMm * MM_TO_PT;
         const originY = yMm * MM_TO_PT;
         const w = widthMm * MM_TO_PT;