Initial implementation of qobuz-qt

- Rust backend (qobuz-backend static lib): Qobuz API client (reqwest/tokio),
  Symphonia audio decoder, CPAL audio output, extern "C" FFI bridge
- Qt 6 frontend mirroring spotify-qt layout: toolbar with playback controls,
  left library dock, central track list, right search panel
- Auth: email/password login with MD5-signed requests; session token persisted
  via QSettings
- Playback: double-click a track → Rust fetches stream URL → Symphonia decodes
  → CPAL outputs to default audio device
- Dark Fusion palette matching spotify-qt feel

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

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.21)
+
+project(qobuz-qt LANGUAGES CXX VERSION 0.1.0)
+
+set(CMAKE_AUTOUIC ON)
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Optional D-Bus support
+option(USE_DBUS "Use D-Bus integration" ON)
+
+# LTO support
+option(USE_LTO "Use link time optimization" OFF)
+
+if (POLICY CMP0072)
+    cmake_policy(SET CMP0072 NEW)
+endif ()
+
+# Find Qt 6
+find_package(Qt6 COMPONENTS Core Widgets Network Gui Svg REQUIRED)
+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)
+
+corrosion_import_crate(MANIFEST_PATH rust/Cargo.toml CRATES qobuz-backend)
+
+# Create main executable
+add_executable(qobuz-qt res.qrc)
+
+# Source files
+add_subdirectory(src)
+
+# Include paths
+target_include_directories(qobuz-qt PRIVATE
+    "${CMAKE_CURRENT_SOURCE_DIR}/src"
+    "${CMAKE_CURRENT_SOURCE_DIR}/rust/include"
+)
+
+# Version / app definitions
+target_compile_definitions(qobuz-qt PRIVATE APP_VERSION="v${PROJECT_VERSION}")
+target_compile_definitions(qobuz-qt PRIVATE APP_NAME="${PROJECT_NAME}")
+
+# Link Qt + Rust backend
+target_link_libraries(qobuz-qt PRIVATE
+    Qt6::Core
+    Qt6::Widgets
+    Qt6::Network
+    Qt6::Gui
+    Qt6::Svg
+    qobuz-backend
+)
+
+# Platform-specific system libs needed by the Rust audio stack (cpal/ALSA)
+if (UNIX AND NOT APPLE)
+    target_link_libraries(qobuz-qt PRIVATE asound)
+endif ()
+
+# Compiler warnings
+if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    target_compile_options(qobuz-qt PRIVATE -Wall -Wextra -Wno-unused-parameter)
+endif ()
+
+# D-Bus
+if (Qt6DBus_FOUND)
+    target_compile_definitions(qobuz-qt PRIVATE USE_DBUS)
+    target_link_libraries(qobuz-qt PRIVATE Qt6::DBus)
+endif ()
+
+# LTO
+if (USE_LTO)
+    include(CheckIPOSupported)
+    check_ipo_supported(RESULT ipo_supported OUTPUT ipo_error)
+    if (ipo_supported AND CMAKE_BUILD_TYPE STREQUAL "Release")
+        set_property(TARGET qobuz-qt PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+    endif ()
+endif ()
+
+# Install
+if (UNIX)
+    install(FILES res/logo/qobuz-qt.svg DESTINATION share/icons/hicolor/scalable/apps)
+    install(FILES res/app/qobuz-qt.desktop DESTINATION share/applications)
+    install(TARGETS qobuz-qt RUNTIME DESTINATION bin)
+endif ()