feat(skann): markera troliga dubbletter i granskningen innan bekraftelse

Enligt Johans onskan: appen forstar sjalv nar en vara troligen redan finns
(samma katalog-id ELLER liknande namn, aven om AI:n laser den olika fran en
annan vinkel) och markerar den i skann-granskningen. Hog sakerhet (>=0.7) =
avmarkerad som standard men syns tydligt och gar att angra; lagre = markerad
men kvar sa du valjer. Jamfor bade mot aktivt lager och tidigare varor i samma
skanning. Ingen auto-hopslagning utan bekraftelse (spec 9). GET /v1/scans/:id
annoterar varje forslag med possibleDuplicate {name, reason, score}.

apps/api/src/routes/scans.ts

@@ -7,7 +7,7 @@ import { confirmScanInputSchema, createScanInputSchema, idParamSchema } from "@a
 import { errors, parse } from "../lib/errors.js";
 import { emitEvent, requireActiveHousehold } from "../lib/helpers.js";
 import { consumeAiScan } from "../lib/entitlements.js";
-import { normalizeItemName } from "@app/inventory-engine";
+import { findDuplicateCandidates, normalizeItemName } from "@app/inventory-engine";
 
 /**
  * Skanningsflödet (spec §50):
@@ -125,7 +125,8 @@ export async function scanRoutes(app: FastifyInstance) {
 
   app.get("/v1/scans/:id", auth, async (req) => {
     const { id } = parse(idParamSchema, req.params);
-    return getOwnedScan(app, id, req.userId);
+    const job = await getOwnedScan(app, id, req.userId);
+    return annotateScanDuplicates(app, job);
   });
 
   app.post("/v1/scans/:id/confirm", auth, async (req) => {
@@ -293,6 +294,79 @@ async function getOwnedScan(app: FastifyInstance, id: string, userId: string) {
   return job;
 }
 
+/**
+ * Flaggar troliga dubbletter i ett skann-resultat INNAN användaren bekräftar:
+ * jämför varje föreslagen vara mot aktivt lager OCH mot tidigare varor i samma
+ * skanning (så samma hylla från två vinklar fångas). Ren hint – appen slår
+ * aldrig ihop utan bekräftelse (spec §9); användaren väljer i granskningen.
+ */
+async function annotateScanDuplicates(
+  app: FastifyInstance,
+  job: Awaited<ReturnType<typeof getOwnedScan>>,
+) {
+  const result = job.result as { items?: Array<Record<string, unknown>> } | null;
+  if (!result?.items?.length || !job.householdId) return job;
+
+  const rows = await app.db
+    .select({
+      id: schema.inventoryItems.id,
+      canonicalIngredientId: schema.inventoryItems.canonicalIngredientId,
+      displayName: schema.inventoryItems.displayName,
+      brand: schema.inventoryItems.brand,
+      quantity: schema.inventoryItems.quantity,
+      source: schema.inventoryItems.source,
+      createdAt: schema.inventoryItems.createdAt,
+    })
+    .from(schema.inventoryItems)
+    .where(
+      and(
+        eq(schema.inventoryItems.householdId, job.householdId),
+        isNull(schema.inventoryItems.depletedAt),
+        gt(schema.inventoryItems.quantity, 0),
+      ),
+    );
+
+  const existing = rows.map((r) => ({
+    id: r.id,
+    canonicalIngredientId: r.canonicalIngredientId,
+    displayName: r.displayName,
+    brand: r.brand,
+    quantity: Number(r.quantity) || 0,
+    source: r.source,
+    createdAt: r.createdAt.toISOString(),
+  }));
+
+  const source = scanSource(job.scanType);
+  const now = new Date().toISOString();
+  const seen: typeof existing = [];
+
+  const items = result.items.map((it, idx) => {
+    const input = {
+      canonicalIngredientId: (it.canonicalIngredientId as string | null) ?? null,
+      displayName: String(it.detectedName ?? ""),
+      brand: (it.brand as string | null) ?? null,
+      quantity: typeof it.estimatedQuantity === "number" ? it.estimatedQuantity : 1,
+      source,
+      createdAt: now,
+    };
+    const pool = [...existing, ...seen];
+    const [top] = findDuplicateCandidates(input, pool);
+    seen.push({ id: String(it.tempId ?? idx), ...input });
+    if (!top) return { ...it, possibleDuplicate: null };
+    const match = pool.find((p) => p.id === top.itemId);
+    return {
+      ...it,
+      possibleDuplicate: {
+        name: match?.displayName ?? "",
+        reason: top.reasons[0] ?? "liknande vara",
+        score: top.score,
+      },
+    };
+  });
+
+  return { ...job, result: { ...result, items } };
+}
+
 async function lookupBarcode(app: FastifyInstance, gtin: string) {
   // 1. Egen produktdatabas (aktuell version)
   const [own] = await app.db