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/gamification.ts

@@ -102,7 +102,14 @@ builder.queryField("userGamification", (t) =>
       return {
         stats: stats[0] ? { ...stats[0], rank } : null,
         achievements: userAchievements.map((a) => ({
-          ...a,
+          id: a.id!,
+          code: a.code!,
+          name: a.name!,
+          description: a.description!,
+          icon: a.icon!,
+          category: a.category!,
+          required_count: a.required_count!,
+          progress: a.progress!,
           date_unlocked: a.date_unlocked!,
         })),
         recent_points: recentPoints,