feat: embed native VST GUI in mastering + fx rack panels (bridge --fx-gui frame capture + input relay)

Linux parts (0L1-4L1 per TASKS_LINUX_WINDOWS.md):
- native_bridge: FxGuiServer.cpp HTTP server (Winsock) — /frame BitBlt +
  PrintWindow fallback -> JPEG (libjpeg-turbo q70), /input PostMessage relay
  (mouse/wheel/key, coords scaled), /close, /ping; RenderFxJob fxGuiSetup +
  run_fx_gui_server (offscreen); main.cpp --fx-gui dispatch; vcpkg +
  CMakeLists WIN32-only + JPEG.
- api: open_fx_gui embed flag spawn --fx-gui, parse SF_FXGUI_PORT -> embed_url,
  fx-gui/close endpoint; 4 unit tests.
- ui: VstGuiEmbed component (frame refresh 100ms, ping 2s, input relay,
  scale coords) shared by MasteringModal + FXRackModal; swap graph<->GUI,
  cleanup on unmount, dead-bridge toast fallback.
- docs: TASKS_LINUX_WINDOWS.md, WALKTHROUGH_WINDOWS.md, PLAN status.
Windows tasks 0W1-4W1 remain (build + E2E real VST).

native_bridge/CMakeLists.txt

@@ -59,6 +59,7 @@ add_executable(daw_vst_bridge
   src/main.cpp
   src/RenderJob.cpp
   src/RenderFxJob.cpp
+  src/FxGuiServer.cpp
   src/NativeInstrumentEngine.cpp
   src/SharedMemoryIPC.cpp
   src/Vst3Instrument.cpp
@@ -89,7 +90,8 @@ if(VST3_SDK_TARGET)
   endif()
 endif()
 if(WIN32)
-  target_link_libraries(daw_vst_bridge PRIVATE ${FLUIDSYNTH_LIBRARY} ${SFIZZ_LIBRARY})
+  find_package(JPEG REQUIRED)  # libjpeg-turbo (vcpkg) — FxGuiServer.cpp JPEG encode
+  target_link_libraries(daw_vst_bridge PRIVATE ${FLUIDSYNTH_LIBRARY} ${SFIZZ_LIBRARY} JPEG::JPEG)
   # Required Windows libs
   target_link_libraries(daw_vst_bridge PRIVATE winmm imm32)
 else()