chore: initial project scaffold from architecture design

- Add CLAUDE.md with project overview, tech stack, build commands,
  architecture description, coding standards, and sample images section
- Add full directory structure: src/, docs/, tests/, import/
- Add CMakeLists.txt with C++20, OpenCV/LibRaw/Qt6 dependencies,
  converter_core static lib, optional GUI, and GTest tests
- Add architecture documentation: ARCHITECTURE.md, PIPELINE.md, MODULES.md
- Add source skeletons for all pipeline stages:
  RawLoader, Preprocessor, NegativeDetector, Inverter, ColorCorrector,
  CropProcessor, OutputWriter, Pipeline, MainWindow, CliRunner, main.cpp
- Add initial test stubs for pipeline and rawloader
- Add sample ARW files in import/ for integration testing

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

CMakeLists.txt

@@ -0,0 +1,104 @@
+cmake_minimum_required(VERSION 3.20)
+project(photo-converter
+    VERSION 0.1.0
+    DESCRIPTION "Analog film negative to digital positive converter"
+    LANGUAGES CXX
+)
+
+# ──────────────────────────────────────────────
+# C++ Standard
+# ──────────────────────────────────────────────
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+# ──────────────────────────────────────────────
+# Build options
+# ──────────────────────────────────────────────
+option(BUILD_TESTS "Build unit tests" ON)
+option(BUILD_GUI "Build GUI (requires Qt 6)" ON)
+
+# ──────────────────────────────────────────────
+# Dependencies
+# ──────────────────────────────────────────────
+find_package(OpenCV 4.10 REQUIRED COMPONENTS core imgproc imgcodecs)
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(LIBRAW REQUIRED IMPORTED_TARGET libraw)
+
+if(BUILD_GUI)
+    find_package(Qt6 6.8 REQUIRED COMPONENTS Widgets)
+    qt_standard_project_setup()
+endif()
+
+# ──────────────────────────────────────────────
+# Core converter library (no Qt dependency)
+# ──────────────────────────────────────────────
+add_library(converter_core STATIC
+    src/converter/pipeline/Pipeline.cpp
+    src/converter/rawloader/RawLoader.cpp
+    src/converter/preprocess/Preprocessor.cpp
+    src/converter/negative/NegativeDetector.cpp
+    src/converter/invert/Inverter.cpp
+    src/converter/color/ColorCorrector.cpp
+    src/converter/crop/CropProcessor.cpp
+    src/converter/output/OutputWriter.cpp
+    src/cli/CliRunner.cpp
+)
+
+target_include_directories(converter_core PUBLIC
+    ${CMAKE_CURRENT_SOURCE_DIR}/src
+)
+
+target_link_libraries(converter_core PUBLIC
+    ${OpenCV_LIBS}
+    PkgConfig::LIBRAW
+)
+
+target_compile_options(converter_core PRIVATE
+    $<$<CXX_COMPILER_ID:GNU>:-Wall -Wextra -Wpedantic>
+    $<$<CXX_COMPILER_ID:Clang>:-Wall -Wextra -Wpedantic>
+    $<$<CXX_COMPILER_ID:MSVC>:/W4>
+)
+
+# ──────────────────────────────────────────────
+# Main executable
+# ──────────────────────────────────────────────
+if(BUILD_GUI)
+    qt_add_executable(photo-converter
+        src/main.cpp
+        src/gui/MainWindow.cpp
+        src/gui/MainWindow.h
+    )
+
+    target_link_libraries(photo-converter PRIVATE
+        converter_core
+        Qt6::Widgets
+    )
+
+    target_include_directories(photo-converter PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/src
+    )
+else()
+    # CLI-only build (no Qt)
+    add_executable(photo-converter
+        src/main.cpp
+    )
+
+    target_link_libraries(photo-converter PRIVATE
+        converter_core
+    )
+
+    target_compile_definitions(photo-converter PRIVATE NO_GUI=1)
+
+    target_include_directories(photo-converter PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/src
+    )
+endif()
+
+# ──────────────────────────────────────────────
+# Tests
+# ──────────────────────────────────────────────
+if(BUILD_TESTS)
+    enable_testing()
+    add_subdirectory(tests)
+endif()