feat: add ILLMService interface and implementation for LLM service ab…

…straction

src/llm/CMakeLists.txt

@@ -0,0 +1,15 @@
+# ${CMAKE_SOURCE_DIR}/src/llm/CMakeLists.txt
+add_library(
+    ILLMService
+    STATIC
+    ILLMService.cpp)
+
+target_link_libraries(
+    ILLMService
+    PUBLIC
+    Qt6::Core)
+
+target_include_directories(
+    ILLMService
+    PUBLIC
+    ${CMAKE_CURRENT_LIST_DIR})

src/llm/ILLMService.cpp

@@ -0,0 +1,3 @@
+#include "ILLMService.hpp"
+
+ILLMService::~ILLMService() noexcept = default;

src/llm/ILLMService.hpp

@@ -0,0 +1,16 @@
+#pragma once
+#include <QString>
+
+/**
+ * @brief Interface for LLM service abstraction
+ *
+ * Allows dependency injection and testing without actual LLM calls.
+ */
+class ILLMService {
+public:
+  virtual ~ILLMService() noexcept;
+
+  virtual void sendMessage(const QString& message) = 0;
+  virtual void cancelRequest() = 0;
+  [[nodiscard]] virtual bool isAvailable() const noexcept = 0;
+};