fix: resolve linter errors in Android modules

- Remove unused imports from mobsf_scanner.py (asyncio, hashlib, json, Optional)
- Remove unused variables from opengrep_android.py (start_col, end_col)
- Remove duplicate Path import from workflow.py

backend/toolbox/workflows/android_static_analysis/workflow.py

@@ -129,7 +129,6 @@ class AndroidStaticAnalysisWorkflow:
 
         # Handle case where workspace_path is a file (single APK upload)
         # vs. a directory containing files
-        from pathlib import Path
         workspace_path_obj = Path(workspace_path)
 
         # Determine actual workspace directory and APK path