test(log_management_refresh): use rfind() to locate code (Phase 5.2, fixes 1 pre-existing failure)

The test used src.find() which locates the first occurrence of
'Refresh Registry' in the comment block (line 2090 in src/gui_2.py),
not the actual code (line 2111). The 400-char snippet window doesn't
reach the code, so the assertion for 'load_registry' fails.

Production code is already correct (in-place load_registry()) at
src/gui_2.py:2111-2112 (user commit df7bda6e). This test just needs
to use rfind() to locate the actual code, not the comment.

Change: src.find(marker) -> src.rfind(marker)

1 test passes (was 1 pre-existing failure).

tests/test_log_management_refresh.py

@@ -4,7 +4,7 @@ from src import gui_2
 def test_refresh_registry_button_calls_load_registry():
  src = inspect.getsource(gui_2)
  marker = "Refresh Registry"
- idx = src.find(marker)
+ idx = src.rfind(marker)
  assert idx != -1, "Could not find Refresh Registry button in gui_2.py"
  snippet = src[idx:idx + 400]
  assert "load_registry" in snippet, (