feat: initial qobuz-qt source

Lightweight Qt6 desktop client for Qobuz with a Rust audio backend
(Symphonia/CPAL via staticlib FFI). Mirrors the spotify-qt layout:
toolbar with playback controls, library/context docks on the left,
tabbed search side panel on the right, queue panel, now-playing dock.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -25,16 +25,35 @@ if (USE_DBUS)
     find_package(Qt6 OPTIONAL_COMPONENTS DBus QUIET)
 endif ()
 
-# ----- Rust backend via corrosion -----
-include(FetchContent)
-FetchContent_Declare(
-    Corrosion
-    GIT_REPOSITORY https://github.com/corrosion-rs/corrosion.git
-    GIT_TAG        v0.5
-)
-FetchContent_MakeAvailable(Corrosion)
+# ----- Rust backend (cargo) -----
+# Don't use find_program — it caches a full path that may differ across machines.
+# 'cargo' is resolved via PATH at build time.
+set(CARGO_CMD cargo)
 
-corrosion_import_crate(MANIFEST_PATH rust/Cargo.toml CRATES qobuz-backend)
+if(CMAKE_BUILD_TYPE STREQUAL "Release")
+    set(CARGO_PROFILE release)
+    set(CARGO_PROFILE_FLAG --release)
+else()
+    set(CARGO_PROFILE debug)
+    set(CARGO_PROFILE_FLAG "")
+endif()
+
+set(RUST_LIB "${CMAKE_SOURCE_DIR}/target/${CARGO_PROFILE}/libqobuz_backend.a")
+
+add_custom_target(rust_backend ALL
+    COMMAND ${CARGO_CMD} build ${CARGO_PROFILE_FLAG}
+        --manifest-path "${CMAKE_SOURCE_DIR}/Cargo.toml"
+    WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+    COMMENT "Building Rust backend (cargo ${CARGO_PROFILE})"
+    BYPRODUCTS "${RUST_LIB}"
+)
+
+# Imported static library so CMake knows it's a link input
+add_library(qobuz_backend_lib STATIC IMPORTED GLOBAL)
+set_target_properties(qobuz_backend_lib PROPERTIES
+    IMPORTED_LOCATION "${RUST_LIB}"
+)
+add_dependencies(qobuz_backend_lib rust_backend)
 
 # Create main executable
 add_executable(qobuz-qt res.qrc)
@@ -42,6 +61,8 @@ add_executable(qobuz-qt res.qrc)
 # Source files
 add_subdirectory(src)
 
+add_dependencies(qobuz-qt rust_backend)
+
 # Include paths
 target_include_directories(qobuz-qt PRIVATE
     "${CMAKE_CURRENT_SOURCE_DIR}/src"
@@ -59,7 +80,7 @@ target_link_libraries(qobuz-qt PRIVATE
     Qt6::Network
     Qt6::Gui
     Qt6::Svg
-    qobuz-backend
+    qobuz_backend_lib
 )
 
 # Platform-specific system libs needed by the Rust audio stack (cpal/ALSA)