feat: image core — format math, sharp pipeline, sticker contour, prompts, pg-boss queue+worker

- format.ts: exact px (cm/2.54*dpi), catalog incl. The Frame/portrait, aspect ratio
- pipeline.ts: finalizeToFormat (cover/attention crop, dpi metadata), stickerContour
  (alpha dilation -> white border), heic->png, german filename slug
- prompts.ts: task prompts (clean/cutout/format) — reproduce, don't reinterpret
- process.ts: per-item chain (load -> model /v1/images -> finalize -> contour -> store)
- queue.ts + worker.ts: pg-boss (concurrency, retry, counters, 402 pause, completion)
- verified locally: 30x40@300dpi = exact 3543x4724 + dpi meta; sticker white border + alpha

src/lib/pipeline.ts

@@ -0,0 +1,94 @@
+import sharp from 'sharp';
+import type { Dimensions } from './format';
+
+export type CropMode = 'crop' | 'extend';
+
+/**
+ * Bringt ein (Modell-)Ergebnis exakt auf das Zielmaß und schreibt dpi-Metadaten.
+ * target=null → Original behalten (nur dpi setzen). Erhält Alpha, falls vorhanden.
+ */
+export async function finalizeToFormat(
+  buffer: Buffer,
+  target: Dimensions | null,
+  cropMode: CropMode,
+  dpi: number,
+): Promise<{ buffer: Buffer; width: number; height: number; hasAlpha: boolean }> {
+  let img = sharp(buffer, { failOn: 'none' });
+  const meta = await img.metadata();
+  const hasAlpha = !!meta.hasAlpha;
+
+  if (target) {
+    img = sharp(buffer, { failOn: 'none' }).resize(target.w, target.h, {
+      fit: 'cover',
+      position: cropMode === 'crop' ? sharp.strategy.attention : 'centre',
+    });
+  }
+
+  const out = await img
+    .withMetadata({ density: dpi })
+    .png({ compressionLevel: 9 })
+    .toBuffer({ resolveWithObject: true });
+
+  return { buffer: out.data, width: out.info.width, height: out.info.height, hasAlpha };
+}
+
+/**
+ * Weißer Stickerrand um das freigestellte Motiv (ohne Modell).
+ * Alpha extrahieren → Dilatation (Blur+Threshold) → weiße Konturebene → Original darüber.
+ * Radius = contourMm / 25.4 * dpi.
+ */
+export async function stickerContour(
+  buffer: Buffer,
+  contourMm: number,
+  dpi: number,
+): Promise<Buffer> {
+  const base = sharp(buffer, { failOn: 'none' }).ensureAlpha();
+  const { width, height } = await base.metadata();
+  if (!width || !height) throw new Error('Bildmaße unbekannt');
+
+  const radiusPx = Math.max(1, Math.round((contourMm / 25.4) * dpi));
+
+  // Alpha als Graustufenmaske, per Blur+Threshold verbreitern (Dilatation).
+  const mask = await sharp(buffer, { failOn: 'none' })
+    .ensureAlpha()
+    .extractChannel('alpha')
+    .blur(Math.max(0.3, radiusPx / 2))
+    .threshold(1)
+    .toColourspace('b-w')
+    .raw()
+    .toBuffer();
+
+  // Weiße Ebene, die verbreiterte Maske als Alpha.
+  const whiteLayer = await sharp({
+    create: { width, height, channels: 3, background: { r: 255, g: 255, b: 255 } },
+  })
+    .joinChannel(mask, { raw: { width, height, channels: 1 } })
+    .png()
+    .toBuffer();
+
+  // Original (RGBA) über die Konturebene legen.
+  const original = await base.png().toBuffer();
+  return sharp(whiteLayer)
+    .composite([{ input: original }])
+    .withMetadata({ density: dpi })
+    .png({ compressionLevel: 9 })
+    .toBuffer();
+}
+
+/** HEIC/HEIF → PNG-Puffer (sharp kann HEIC im Standard-Build meist nicht). */
+export async function heicToPng(buffer: Buffer): Promise<Buffer> {
+  const convert = (await import('heic-convert')).default as any;
+  const out = await convert({ buffer, format: 'PNG' });
+  return Buffer.from(out);
+}
+
+/** Deutscher Datei-Slug: klein, mit Bindestrichen, Format angehängt. */
+export function slugFilename(base: string, formatLabel: string, ext = 'png'): string {
+  const slug = (base || 'bild')
+    .toLowerCase()
+    .replace(/[äöüß]/g, (c) => ({ ä: 'ae', ö: 'oe', ü: 'ue', ß: 'ss' }[c] || c))
+    .normalize('NFKD').replace(/[̀-ͯ]/g, '')
+    .replace(/[^a-z0-9]+/g, '-').replace(/^-+|-+$/g, '').slice(0, 60) || 'bild';
+  const fmt = formatLabel.toLowerCase().replace(/[^a-z0-9]+/g, '');
+  return `${slug}${fmt ? '-' + fmt : ''}.${ext}`;
+}