Replace flutter_downloader with file_saver_ffi

[vanvixi]

Replace flutter_downloader with file_saver_ffi for cross-platform downloads

Motivation

flutter_downloader works well on Android/iOS, but its architecture adds significant complexity to the codebase:

• Requires a background isolate with IsolateNameServer and ReceivePort just to receive download callbacks
• Needs a @pragma("vm:entry-point") static callback and manual IsolateNameServer registration/cleanup in initState/dispose
• Desktop downloads had to fall back to a separate http-based implementation with no progress tracking
• Task state must be queried from an internal SQLite DB via loadTasksWithRawQuery
• Contains a workaround for Flutter engine bug #119589

All of this makes ClientWidget hard to understand and maintain.

Solution

This PR replaces flutter_downloader with file_saver_ffi — a cross-platform file saving library that:

• Runs on a native background thread (Swift on iOS/macOS, Kotlin on Android) — no UI blocking, no Dart isolate management needed
• On Windows and Linux, uses pure Dart with chunked I/O so the main thread is never blocked
• Saves files in chunks and reports progress on all platforms
• Wraps everything behind a clean Stream<SaveProgress> API — callers need zero knowledge of threading or platform internals

Key improvements:

	Before	After
Platform support	Android + iOS only (desktop: separate http impl)	Android, iOS, macOS, Windows, Linux
Threading	Manual Dart isolate + IsolateNameServer boilerplate	Handled internally by the library (native threads / chunked Dart)
Progress tracking	Not implemented	Real-time via SaveProgressUpdate(double progress)
Lines removed	—	~100 lines of boilerplate deleted

Changes

• ClientWidget: Removed ReceivePort, IsolateNameServer, _initDownloadModule(), downloadCallback() static method, and 3 unused imports. _downloadStreamListener() is unchanged.
• DownloadService: Replaced two platform-branched download methods with a single startDownloading() using FileSaver.save(). MIME type detected automatically via the existing mime package.
• DownloadEntity: Removed unused id and manner fields; added progress field and copyWith().
• FileProvider: Added in-memory _progressMap + getProgress() for granular progress updates without polluting the Hive entity.
• FileTileClient: Progress indicator now shows determinate progress (0-100%) using Selector<FileProvider, double> with shouldRebuild to avoid full-list rebuilds on every tick.
• Removed download_manner.dart, uuid dependency, and android_path_provider.

Result

The entire download flow — including real-time progress — now works identically on all platforms with significantly less code. Threading and chunk management are handled by file_saver_ffi internally; the app just listens to a stream.

---

Note: file_saver_ffi is published on pub.dev (^0.8.1). No additional native setup is required beyond what Flutter already provides.

[huynguyennovem]

Awsome. Thank you for doing this! Overall looks good to me, except two issues:

1. ios and macos file changes don't relate to this work. Could you please revert them and re-commit the change?
2. After downloading a file, it is no longer possible to open it (please watch the video). I printed the output path and saw that it is something like content://media/external_primary/file/1000000232 now, which seems to be exposed from the file_saver_ffi package, doesn't it? Previously, a file was downloaded and stored to AndroidPathProvider.downloadsPath. I also see it's AndroidSaveLocation.downloads on Android by default in package file_saver_ffi. Not sure if these two paths are the same. Could you please check this?

Screen.Recording.2026-03-07.at.17.01.34.mov