Precharge les mappings IMDb au warmup (1.27s -> 16ms sur le premier appel /api?t=imdb)

lib/imdbMapping.js

@@ -33,3 +33,12 @@ export async function lookupImdb(imdbId) {
   }
   return null;
 }
+
+// Eager-load both mappings — used at server startup to remove the first-request
+// 1s latency. Returns the number of entries loaded per type.
+export async function preloadMappings() {
+  const out = { movie: 0, tv: 0 };
+  try { out.movie = (await loadOne('movie')).size; } catch { /* missing */ }
+  try { out.tv = (await loadOne('tv')).size; } catch { /* missing */ }
+  return out;
+}