Add native self-hosted instance connection to fluxer_desktop

Trimmed monorepo checkout (fluxer_desktop + packages/voice_engine_v2 +
tools/ci) with a "Connect to a Different Server" menu item and popout
that lets the desktop app switch to any self-hosted Fluxer instance,
plus fixes for well-known discovery on single-domain self-hosted
deployments and a false-positive ERR_ABORTED on same-origin client
redirects during the switch. Defaults to chat.fluxr.chat and uses an
isolated userData directory from the official build.

fluxer_desktop/native/win-game-capture/test-apps/d3d12-present-fixture/Cargo.toml

@@ -0,0 +1,31 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+[package]
+name = "d3d12-present-fixture"
+version = "0.0.0"
+edition = "2024"
+license = "AGPL-3.0-or-later"
+publish = false
+
+# Empty workspace table keeps this fixture out of any parent Cargo workspace,
+# matching the sibling crates (hook/, vulkan-layer/) in this package.
+[workspace]
+resolver = "2"
+
+[[bin]]
+name = "d3d12-present-fixture"
+path = "src/main.rs"
+
+[target.'cfg(target_os = "windows")'.dependencies]
+windows = {version = "0.62.2", features = [
+    "Win32_Foundation",
+    "Win32_Graphics_Direct3D",
+    "Win32_Graphics_Direct3D12",
+    "Win32_Graphics_Dxgi",
+    "Win32_Graphics_Dxgi_Common",
+    "Win32_Graphics_Gdi",
+    "Win32_Security",
+    "Win32_System_LibraryLoader",
+    "Win32_System_Threading",
+    "Win32_UI_WindowsAndMessaging",
+]}
+windows-core = "0.62.2"