fix: accept datetime ranges in parse_date_range

With period.dynamic: true and period.precision: datetime, running
without --date crashed: compute_next_period() returns a datetime range
(YYYY-MM-DDTHH:MM:SS), which parse_date_range() rejected with a
fullmatch against YYYY-MM-DD only.

parse_date_range now accepts YYYY-MM-DDTHH:MM:SS--YYYY-MM-DDTHH:MM:SS
in addition to plain date ranges, returning datetime strings unchanged
(pass-through, matching compute_next_period output). Mixed-precision
ranges, invalid times and reversed ranges are still rejected with the
existing error messages; date-range behavior is unchanged.

Closes #59

redmine_reporter/cli.py

@@ -25,20 +25,27 @@ def parse_date_range(date_arg: str) -> tuple[str, str]:
 
     from_date, to_date = parts[0].strip(), parts[1].strip()
     date_pattern = r"\d{4}-\d{2}-\d{2}"
-    if not re.fullmatch(date_pattern, from_date) or not re.fullmatch(
-        date_pattern, to_date
+    datetime_pattern = r"\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}"
+    if re.fullmatch(date_pattern, from_date) and re.fullmatch(date_pattern, to_date):
+        fmt = "%Y-%m-%d"
+    elif re.fullmatch(datetime_pattern, from_date) and re.fullmatch(
+        datetime_pattern, to_date
     ):
+        fmt = "%Y-%m-%dT%H:%M:%S"
+    else:
         raise ValueError("Date range must be in format YYYY-MM-DD--YYYY-MM-DD")
 
     try:
-        start = datetime.strptime(from_date, "%Y-%m-%d").date()
-        end = datetime.strptime(to_date, "%Y-%m-%d").date()
+        start = datetime.strptime(from_date, fmt)
+        end = datetime.strptime(to_date, fmt)
     except ValueError as e:
         raise ValueError("Date range contains invalid calendar date") from e
 
     if start > end:
         raise ValueError("Date range start must be less than or equal to end")
 
+    if fmt == "%Y-%m-%d":
+        return start.date().isoformat(), end.date().isoformat()
     return start.isoformat(), end.isoformat()