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)

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

routes/chat_helpers.py

@@ -121,7 +121,7 @@ def needs_auto_name(name: str) -> bool:
     if name.startswith("Chat:") or name == "Chat":
         return True
     # Default frontend name: "modelname HH:MM:SS AM/PM"
-    if re.match(r'^.+ \d{1,2}:\d{2}:\d{2}\s*(AM|PM)$', name):
+    if re.match(r"^.+ \d{1,2}:\d{2}:\d{2}(\s*(AM|PM))?$", name, re.IGNORECASE):
         return True
     return False