Fixes#1630.
Debrid downloads currently buffer entire files in RAM. The four clients
now opt into a spooled temporary file: downloads up to 8 MiB stay in
memory, and larger downloads roll to disk. The clients copy from the
file in chunks and close it after use. Other download_url callers retain
the existing BytesIO behavior.
Temporary files are closed on unsuccessful attempts and cancellation;
successful resumed downloads remain open for their caller. Added offline
coverage for disk rollover, timeout cleanup, and resumed content.
Updated the Debrid-Link test doubles for the new opt-in argument.
Validation: 113 tests passed across test_http_download_url,
test_debridlink_client, and test_torbox_client; Ruff check and format
check passed for changed files; git diff --check passed. No live debrid
services were exercised. AI assistance was used in implementing this
change.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
<!-- coderabbit-ai-generated:v1 -->
## Summary by CodeRabbit
* **Improvements**
* Large downloads are handled more efficiently, reducing memory use
while preserving download and resume behavior.
* **Bug Fixes**
* Temporary download data is cleaned up when a download is cancelled or
fails, helping prevent unnecessary resource usage.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
