Add scheduler integration tests

- Created tests/integration/test_scheduler_workflow.py
  * 11 comprehensive integration tests all passing
  * Test full scheduler workflows end-to-end
  * Test database updates during scheduled rescans
  * Test configuration changes apply immediately
  * Test scheduler persistence across restarts
  * Test concurrent scan conflict resolution
  * Test error recovery and edge cases

- Updated docs/instructions.md
  * Marked scheduler integration tests as completed
  * Documented 11/11 passing tests

docs/instructions.md

@@ -166,12 +166,18 @@ For each task completed:
     - Coverage: 100% of test scenarios passing (26/26 tests) 🎉
     - Implementation: Full scheduler service with interval-based scheduling, conflict prevention, and WebSocket notifications
 
-- [ ] **Create tests/integration/test_scheduler_workflow.py** - End-to-end scheduler tests
-    - Test scheduler trigger → library rescan → database update workflow
-    - Test scheduler configuration changes apply immediately
-    - Test scheduler persistence after application restart
-    - Test concurrent manual and automated scan handling
-    - Target: Full workflow validation
+- [x] **Create tests/integration/test_scheduler_workflow.py** - End-to-end scheduler tests ✅
+    - ✅ Test scheduler trigger → library rescan → database update workflow
+    - ✅ Test scheduler configuration changes apply immediately
+    - ✅ Test scheduler persistence after application restart
+    - ✅ Test concurrent manual and automated scan handling
+    - ✅ Test full workflow: trigger → rescan → update → notify
+    - ✅ Test multiple sequential rescans
+    - ✅ Test scheduler status accuracy during workflow
+    - ✅ Test rapid enable/disable cycles
+    - ✅ Test interval change during active scan
+    - Coverage: 100% of integration tests passing (11/11 tests) 🎉
+    - Target: Full workflow validation ✅ COMPLETED
 
 
 - [x] **Fixed NFO batch creation endpoint** in tests/api/test_nfo_endpoints.py