feat: persist metafield resolutions across sessions

Les associations colonne→métachamp sont sauvegardées dans data/metafield-resolutions.json
et rechargées automatiquement à la prochaine création de produits.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/resolutionCache.ts

@@ -0,0 +1,20 @@
+import { readFile, writeFile, mkdir } from 'fs/promises'
+import { join } from 'path'
+import type { MetafieldResolution } from '@/types/creation'
+
+const CACHE_DIR = join(process.cwd(), 'data')
+const CACHE_FILE = join(CACHE_DIR, 'metafield-resolutions.json')
+
+export async function loadResolutionCache(): Promise<Record<string, MetafieldResolution>> {
+  try {
+    const raw = await readFile(CACHE_FILE, 'utf-8')
+    return JSON.parse(raw) as Record<string, MetafieldResolution>
+  } catch {
+    return {}
+  }
+}
+
+export async function saveResolutionCache(cache: Record<string, MetafieldResolution>): Promise<void> {
+  await mkdir(CACHE_DIR, { recursive: true })
+  await writeFile(CACHE_FILE, JSON.stringify(cache, null, 2), 'utf-8')
+}