feat: add imageSourceUrl column to items and threadCandidates

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/db/schema.ts

@@ -20,6 +20,7 @@ export const items = sqliteTable("items", {
 	notes: text("notes"),
 	productUrl: text("product_url"),
 	imageFilename: text("image_filename"),
+	imageSourceUrl: text("image_source_url"),
 	createdAt: integer("created_at", { mode: "timestamp" })
 		.notNull()
 		.$defaultFn(() => new Date()),
@@ -58,6 +59,7 @@ export const threadCandidates = sqliteTable("thread_candidates", {
 	notes: text("notes"),
 	productUrl: text("product_url"),
 	imageFilename: text("image_filename"),
+	imageSourceUrl: text("image_source_url"),
 	status: text("status").notNull().default("researching"),
 	pros: text("pros"),
 	cons: text("cons"),