feat(19-02): add catalog-linked candidates, branched resolution, remove link/unlink routes

- getThreadWithCandidates LEFT JOINs globalItems with COALESCE for name, weight, price, image
- createCandidate accepts and stores globalItemId
- resolveThread branches: reference item (globalItemId set) vs standalone (full data copy)
- Removed link/unlink endpoints from items route (replaced by direct globalItemId FK)
- 6 new tests for catalog-linked candidates and branched resolution

src/server/services/thread.service.ts

@@ -2,6 +2,7 @@ import { and, asc, desc, eq, max, sql } from "drizzle-orm";
 import type { db as prodDb } from "../../db/index.ts";
 import {
 	categories,
+	globalItems,
 	items,
 	threadCandidates,
 	threads,
@@ -79,17 +80,33 @@ export async function getThreadWithCandidates(
 		.select({
 			id: threadCandidates.id,
 			threadId: threadCandidates.threadId,
-			name: threadCandidates.name,
-			weightGrams: threadCandidates.weightGrams,
-			priceCents: threadCandidates.priceCents,
+			name: sql<string>`COALESCE(
+				CASE WHEN ${threadCandidates.globalItemId} IS NOT NULL
+					THEN ${globalItems.brand} || ' ' || ${globalItems.model}
+					ELSE ${threadCandidates.name}
+				END,
+				${threadCandidates.name}
+			)`.as("name"),
+			weightGrams: sql<number | null>`COALESCE(
+				CASE WHEN ${threadCandidates.globalItemId} IS NOT NULL THEN ${globalItems.weightGrams} ELSE NULL END,
+				${threadCandidates.weightGrams}
+			)`.as("weight_grams"),
+			priceCents: sql<number | null>`COALESCE(
+				CASE WHEN ${threadCandidates.globalItemId} IS NOT NULL THEN ${globalItems.priceCents} ELSE NULL END,
+				${threadCandidates.priceCents}
+			)`.as("price_cents"),
 			categoryId: threadCandidates.categoryId,
 			notes: threadCandidates.notes,
 			productUrl: threadCandidates.productUrl,
-			imageFilename: threadCandidates.imageFilename,
+			imageFilename: sql<string | null>`COALESCE(
+				${threadCandidates.imageFilename},
+				CASE WHEN ${threadCandidates.globalItemId} IS NOT NULL THEN ${globalItems.imageUrl} ELSE NULL END
+			)`.as("image_filename"),
 			imageSourceUrl: threadCandidates.imageSourceUrl,
 			status: threadCandidates.status,
 			pros: threadCandidates.pros,
 			cons: threadCandidates.cons,
+			globalItemId: threadCandidates.globalItemId,
 			createdAt: threadCandidates.createdAt,
 			updatedAt: threadCandidates.updatedAt,
 			categoryName: categories.name,
@@ -97,6 +114,7 @@ export async function getThreadWithCandidates(
 		})
 		.from(threadCandidates)
 		.innerJoin(categories, eq(threadCandidates.categoryId, categories.id))
+		.leftJoin(globalItems, eq(threadCandidates.globalItemId, globalItems.id))
 		.where(eq(threadCandidates.threadId, threadId))
 		.orderBy(asc(threadCandidates.sortOrder));
 
@@ -190,6 +208,7 @@ export async function createCandidate(
 			pros: data.pros ?? null,
 			cons: data.cons ?? null,
 			sortOrder: nextSortOrder,
+			globalItemId: data.globalItemId ?? null,
 		})
 		.returning();
 
@@ -332,10 +351,30 @@ export async function resolveThread(
 			? candidate.categoryId
 			: await getOrCreateUncategorized(tx as unknown as Db, userId);
 
-		// 4. Create collection item from candidate data — with userId
-		const [newItem] = await tx
-			.insert(items)
-			.values({
+		// 4. Create collection item — branched on catalog link
+		let insertValues: Record<string, unknown>;
+		if (candidate.globalItemId) {
+			// Reference item — link to global, personal fields only
+			const [gi] = await tx
+				.select()
+				.from(globalItems)
+				.where(eq(globalItems.id, candidate.globalItemId));
+			const fallbackName = gi
+				? `${gi.brand} ${gi.model}`
+				: candidate.name;
+			insertValues = {
+				name: fallbackName,
+				globalItemId: candidate.globalItemId,
+				categoryId: safeCategoryId,
+				userId,
+				notes: candidate.notes,
+				imageFilename: candidate.imageFilename,
+				imageSourceUrl: candidate.imageSourceUrl,
+				quantity: 1,
+			};
+		} else {
+			// Standalone item — full data copy (existing behavior)
+			insertValues = {
 				name: candidate.name,
 				weightGrams: candidate.weightGrams,
 				priceCents: candidate.priceCents,
@@ -346,7 +385,11 @@ export async function resolveThread(
 				imageFilename: candidate.imageFilename,
 				imageSourceUrl: candidate.imageSourceUrl,
 				quantity: 1,
-			})
+			};
+		}
+		const [newItem] = await tx
+			.insert(items)
+			.values(insertValues as any)
 			.returning();
 
 		// 5. Archive the thread