fix: make CapturedRange start/end date filters inclusive

[himewel]

Summary

Same-day captured_range filters (e.g. start=2024-01-07, end=2024-01-07) were serialized as identical midnights (…T00:00:00.000Z,…T00:00:00.000Z). The GoPro cloud API treats that window as half-open [start, end), so the result was an empty media array.

Changes

• In CapturedRange._serialize_captured_range, use the calendar date portion only (also fixes a double-T bug when the datetime already had a time).
• Advance the serialized end by one day so the caller's end date is inclusive.
• Align docs/examples with inclusive calendar-day semantics (--start 2026-03-01 --end 2026-03-01 for a single day).

Example

CapturedRange(
    start=datetime.fromisoformat("2024-01-07"),
    end=datetime.fromisoformat("2024-01-07"),
).model_dump()
# -> "2024-01-07T00:00:00.000Z,2024-01-08T00:00:00.000Z"