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/webrtc-sender/vendor/webrtc-sys/compile_flags.txt

@@ -0,0 +1,22 @@
+-xc++
+-xobjective-c
+-xobjective-c++
+-std=c++17
+-Iinclude
+-Ilibwebrtc/src
+-Ilibwebrtc/src/third_party/abseil-cpp
+-Ilibwebrtc/src/third_party/libc++
+-Ilibwebrtc/src/third_party/libyuv/include
+-Ilibwebrtc/src/sdk/objc/base
+-Ilibwebrtc/src/sdk/objc
+-I../target/cxxbridge
+-DWEBRTC_POSIX
+-DWEBRTC_ANDROID
+-DNDEBUG
+-DWEBRTC_ENABLE_SYMBOL_EXPORT
+-DWEBRTC_APM_DEBUG_DUMP=0
+-D__ANDROID_API__=29
+-DWEBRTC_LIBRARY_IMPL
+--sysroot=/Users/theomonnom/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/sysroot
+--target=aarch64-none-linux-android
+--gcc-toolchain=/Users/theomonnom/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64