chore(test): Centralize app_instance and mock_app fixtures in conftest.py

conductor/tracks.md

@@ -4,6 +4,13 @@ This file tracks all major tracks for the project. Each track has its own detail
 
 ---
 
+## Current Tracks
+
+- [~] **Track: Tech Debt & Test Discipline Cleanup**
+*Link: [./tracks/tech_debt_and_test_cleanup_20260302/](./tracks/tech_debt_and_test_cleanup_20260302/)*
+
+---
+
 ## Completed / Archived
 
 - [x] **Track: Conductor Workflow Improvements**