Enhance Samsung monitor detection logic and add unit tests for trigger candidate selection

tests/test_hardware.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from app.hardware import _select_trigger_candidate_index
+
+
+def test_select_trigger_candidate_by_unique_trigger_code() -> None:
+    candidates = [
+        ("DELL U2720Q", 60),
+        ("Generic PnP Monitor", 19),
+    ]
+    assert _select_trigger_candidate_index(candidates) == 1
+
+
+def test_select_trigger_candidate_by_generic_tiebreaker() -> None:
+    candidates = [
+        ("DELL U2720Q", 15),
+        ("Generic PnP Monitor", 19),
+    ]
+    assert _select_trigger_candidate_index(candidates) == 1
+
+
+def test_select_trigger_candidate_none_when_still_ambiguous() -> None:
+    candidates = [
+        ("Generic PnP Monitor #1", 15),
+        ("Generic PnP Monitor #2", 19),
+    ]
+    assert _select_trigger_candidate_index(candidates) is None