Fix year extraction in research queries

* fix: extract full year in research query entities, not just the century

* fix: same year capture-group bug in the services search copy

* test: research query extracts the full year

tests/test_search_query.py

@@ -0,0 +1,21 @@
+"""Tests for research query entity extraction (src/search/query.py)."""
+
+from src.search.query import _extract_entities
+
+
+def test_extracts_full_four_digit_year():
+    # Regression: the year pattern used a capturing group `(19|20)`, so
+    # re.findall returned just the century ("20") instead of the full year.
+    entities = _extract_entities("What happened to OpenAI in 2024")
+    assert "2024" in entities["dates"]
+    assert "20" not in entities["dates"]
+
+
+def test_extracts_multiple_years():
+    entities = _extract_entities("Compare revenue in 1999 and 2008")
+    assert entities["dates"] == ["1999", "2008"]
+
+
+def test_no_false_year_from_other_numbers():
+    entities = _extract_entities("Top 50 albums of all time")
+    assert entities["dates"] == []