modelgen: recurse through nested generics in list resolvers

_get_list_inner (Pydantic) and _resolve_ts_list (TypeScript) collapsed
nested generics to "str" / "string[]" — so List[List[int]] became
List[str] and List[Dict[str,Any]] became List[str]. Fix recurses on
list-of-list and falls back to Dict[str,Any] / Record<string,unknown>
for list-of-dict.

Regenerated outputs:
- core/gpu/models/models.py: SegmentFieldResponse.boundary now
  List[List[int]], unblocking /segment_field which was 500ing on every
  request with pydantic ValidationError
- core/db/models.py + ui/common/types/generated.ts: Brand.airings now
  matches its source schema (List[Dict[str,Any]] / Record<string,unknown>[])

ui/common/types/generated.ts

@@ -117,7 +117,7 @@ export interface Brand {
   aliases: string[];
   source: BrandSource;
   confirmed: boolean;
-  airings: string[];
+  airings: Record<string, unknown>[];
   total_airings: number;
   created_at: string | null;
   updated_at: string | null;