fix: auto-naming for 24h time format (#1374)

* fix: auto-naming for 24h time format

needs_auto_name() required AM/PM suffix for default
frontend-generated names like 'deepseek-v4-flash 17:46:02'.
Frontend uses toLocaleTimeString() which outputs 24h
format in most locales — so the regex never matched and
auto-naming silently skipped.

Made AM/PM optional and added re.IGNORECASE for 'am'/'pm'.

* test: add regression tests for needs_auto_name (24h + 12h + custom)

---------

Co-authored-by: Calculator Dev <dev@calculator.local>

tests/test_chat_helpers.py

@@ -0,0 +1,29 @@
+import pytest
+from routes.chat_helpers import needs_auto_name
+
+
+@pytest.mark.parametrize("name,expected", [
+    # 24h format (the bug this PR fixes)
+    ("deepseek-v4-flash 14:05:33", True),
+    ("qwq 17:46:02", True),
+    ("gemma3 23:59:59", True),
+    ("claude-sonnet 4 0:00:00", True),
+
+    # 12h format (was already working)
+    ("deepseek-v4-flash 2:05:33 PM", True),
+    ("qwq 06:46:02 AM", True),
+    ("claude-sonnet-4 8:05:17 am", True),
+
+    # empty / default
+    ("", True),
+    ("  ", False),
+    ("Chat: something", True),
+
+    # custom titles – should NOT trigger auto-naming
+    ("custom title", False),
+    ("CW Decoder for STM32", False),
+    ("my chat about python", False),
+    ("Fix the login bug", False),
+])
+def test_needs_auto_name(name, expected):
+    assert needs_auto_name(name) == expected, f"needs_auto_name({name!r}) should be {expected}"