fix(stats): preserve season boundaries during AniList merge resolution

- Allow manual cross-season reassignment without merging entries
- Require validated title matches for automatic merges
- Share title normalization across AniList and stats flows

src/core/utils/title-normalization.ts

@@ -0,0 +1,8 @@
+export function normalizeTitleIdentity(title: string): string {
+  return title
+    .normalize('NFKC')
+    .toLowerCase()
+    .replace(/[^\p{L}\p{N}]+/gu, ' ')
+    .trim()
+    .replace(/\s+/g, ' ');
+}