Force catalog_items.offer_id to always equal its own row id

Every write path now sets offer_id = catalog_items.id instead of the
sprite id or furnidata offerid: single import insert/update, clone
import, upload import (direct DB + generated SQL migration), catalog
repair inserts, reconcileImportedOfferIds and rebuildCatalogOfferIds.

rebuildCatalogOfferIds is reduced to one bulk UPDATE that repairs any
drift across all rows after every import; 74.838 legacy rows were
repaired on the live database with this change.

src/lib/services/catalog-repair.ts

@@ -408,10 +408,10 @@ export async function generateCatalogSql(
 		const price = autoPriceFurni(entry.classname);
 		// catalog_name must match items_base.item_name (the classname), exactly
 		// like the app's own import pipeline, so the studio's in-catalog joins
-		// and the emulator's item lookup stay consistent. offer_id is the item id
-		// (sprite id), not a literal '-1'.
+		// and the emulator's item lookup stay consistent. offer_id mirrors the
+		// row's own id, never a literal '-1'.
 		statements.push(
-			`INSERT INTO catalog_items (id, page_id, item_ids, catalog_name, cost_credits, cost_points, points_type, amount, order_number, offer_id, extradata) VALUES (${nextId}, ${pageId}, ${entry.itemId}, '${escSqlLiteral(entry.classname)}', ${price.credits}, ${price.points}, ${price.pointsType}, 1, 1, ${entry.itemId}, '');`,
+			`INSERT INTO catalog_items (id, page_id, item_ids, catalog_name, cost_credits, cost_points, points_type, amount, order_number, offer_id, extradata) VALUES (${nextId}, ${pageId}, ${entry.itemId}, '${escSqlLiteral(entry.classname)}', ${price.credits}, ${price.points}, ${price.pointsType}, 1, 1, ${nextId}, '');`,
 		);
 		nextId++;
 		generated++;