Simplify frame filtering logic in year_limited decorator

[Tijoxa]

Replace separate first-frame tracking with check against frames list. Filter subsequent frames by comparing against the last frame's max index instead of using start/end bounds, and only append non-empty results.

Fixes #388

Since all the queries return DatetimeIndex, we can just select datetimes that are greater thant the last max index.

But to ensure that this is the case, we can do additional checks:

if not frames or not isinstance(df.index, pd.DatetimeIndex):
    interval_mask = frame.index
else:
    interval_mask = frame.index > max(frames[-1].index)