Port two upstream PRs:
- PR #1207: Replace manual chunked download loop with
HTTPClient::writeToStream via a FileWriteStream adapter, improving
reliability for OPDS file downloads including chunked transfers.
- PR #1209: Add support for multiple OPDS servers with a new
OpdsServerStore (JSON persistence with MAC-based password obfuscation),
OpdsServerListActivity and OpdsSettingsActivity UIs, per-server
credentials passed to HttpDownloader, web UI management endpoints,
and migration from legacy single-server settings.
Made-with: Cursor
2aa13ea2de
