fix: resolve TypeScript build errors from leftJoin nullable types

Non-null assert photo/achievement ids that are structurally non-null
due to FK constraints but nullable in Drizzle's leftJoin return type.
Add missing description field to enrichVideo model select and map.

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

packages/backend/src/graphql/resolvers/users.ts

@@ -195,8 +195,8 @@ builder.queryField("adminGetUser", (t) =>
         .orderBy(user_photos.sort);
       const seen = new Set<string>();
       const photos = photoRows
-        .filter((p) => p.id && !seen.has(p.id) && seen.add(p.id))
-        .map((p) => ({ id: p.id, filename: p.filename }));
+        .filter((p) => p.id !== null && !seen.has(p.id!) && seen.add(p.id!))
+        .map((p) => ({ id: p.id!, filename: p.filename! }));
       return { ...user[0], photos };
     },
   }),