feat: re-profile 22 emulators, refactor validation to common.py

batch re-profiled nekop2 through pokemini. mupen64plus renamed to
mupen64plus_next. new profiles: nes, mupen64plus_next.
validation functions (_build_validation_index, check_file_validation)
consolidated in common.py — single source of truth for verify.py
and generate_pack.py. pipeline 100% consistent on all 6 platforms.

scripts/validate_pr.py

@@ -93,7 +93,10 @@ class ValidationResult:
 def load_database(db_path: str) -> dict | None:
     try:
         return _load_database(db_path)
-    except (FileNotFoundError, json.JSONDecodeError):
+    except FileNotFoundError:
+        return None
+    except json.JSONDecodeError as e:
+        print(f"WARNING: corrupt database.json: {e}", file=sys.stderr)
         return None