RatioMaster.NET 2.0.0

Full rewrite from WinForms / .NET Framework 4.8 to Avalonia 12 / .NET 11.

• UI rewritten — dark Fluent interface, MVVM with compiled bindings, tabs for running several
  torrents at once, a live upload graph, and a status line that reports the session state (tracker
  OK / empty swarm / error) with a matching colour on each tab. Layout adapts down to phone width.
• Pure emulation — the legacy "read the torrent client's process memory" path is gone, so no
  client needs to be installed or running and none is ever touched. RatioMaster can run alongside a
  real client; if the emulated listening port is already taken it degrades instead of failing.
• Client profiles rebuilt — kept only currently-deployed clients, each checked against what the
  real client sends: qBittorrent (default), µTorrent, Transmission and Deluge. Dropped BitTorrent
  6.0.3, Vuze, KTorrent and BitComet. Corrected the announce key case, µTorrent's partly hardcoded
  peer_id tail (a fingerprint shared by every user), and Transmission's peer_id, which requires
  a base-36 checksum a tracker can verify.
• Engine hardening — announces are time-bounded, bencode parsing survives truncated files,
  redirects resolve correctly, IPv6 peer lists (BEP 7) are supported, and the engine never
  overwrites your own settings.
• Portable session — tabs, speeds and counters are restored on the next launch. Launching a
  second time re-opens the running window instead of starting a competing process.
• Android support — the same UI ships as an APK/AAB.
• One build script — Installer\build_RatioMaster_setup.bat produces a single-file Windows
  executable (Native AOT, Skia statically linked), a win-arm64 zip, Linux AppImages for x86_64 and
  aarch64, and the Android packages.