style(cli): improve type hinting consistency in merge_json_files

Author: RbBtSn0w

src/specify_cli/__init__.py

@@ -684,7 +684,7 @@ def log(message, color="green"):
             shutil.copy2(sub_item, dest_file)
 
 
-def merge_json_files(existing_path: Path, new_content: Any, verbose: bool = False) -> Optional[dict]:
+def merge_json_files(existing_path: Path, new_content: Any, verbose: bool = False) -> Optional[dict[str, Any]]:
     """Merge new JSON content into existing JSON file.
 
     Performs a polite deep merge where:
@@ -732,7 +732,8 @@ def merge_json_files(existing_path: Path, new_content: Any, verbose: bool = Fals
         if verbose:
             console.print(f"[yellow]Warning: Existing JSON in {existing_path.name} is not an object. Skipping merge to avoid data loss.[/yellow]")
         return None
-    def deep_merge_polite(base: dict, update: dict) -> dict:
+
+    def deep_merge_polite(base: dict[str, Any], update: dict[str, Any]) -> dict[str, Any]:
         """Recursively merge update dict into base dict, preserving base values."""
         result = base.copy()
         for key, value in update.items():