chore(pack): add CPack configuration to build a deb package

Add install rules and CPack settings so cpack produces an installable
.deb. Dependencies are derived with dpkg-shlibdeps, so they follow the
binaries. The sherpa-onnx runtime the streaming backend needs is bundled
because no distro package provides it. The fetch-models script now also
locates its registry when installed system-wide.

增加 CPack 配置，可直接用 cpack 打出 deb：安装规则含桌面入口、应用图标、
模型注册表与下载脚本、用户文档；依赖由 dpkg-shlibdeps 自动推导；流式后端
需要的 sherpa-onnx 运行时（发行版无对应包）随包携带；fetch-models 脚本
装到系统后也能找到注册表。

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.24)
-project(live-caption LANGUAGES CXX)
+project(live-caption VERSION 0.1.0 LANGUAGES CXX)
 
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
@@ -153,8 +153,31 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
     endforeach()
 endif()
 
+# ---------------------------------------------------------------------------
+# 安装后的 RPATH
+#
+# 1) $ORIGIN/../<私有库目录>：打包时随包携带的 sherpa-onnx 运行时（lib/ 下的相对路径）；
+# 2) llama / mtmd：发行版把这两个库放在 .../llama 子目录，而该目录不在 ld 的默认搜索
+#    路径里（ldconfig -p 里看不到），所以必须显式写进 RPATH，否则安装后起不来。
+# ---------------------------------------------------------------------------
+set(LC_PRIVATE_LIBDIR "lib/live-caption")
+set(_lc_install_rpath "\$ORIGIN/../${LC_PRIVATE_LIBDIR}")
+get_filename_component(_lc_llama_dir "${LC_MTMD_LIB}" DIRECTORY)
+if(IS_DIRECTORY "${_lc_llama_dir}")
+    list(APPEND _lc_install_rpath "${_lc_llama_dir}")
+endif()
+set_target_properties(live-caption live-caption-cli PROPERTIES
+    INSTALL_RPATH                 "${_lc_install_rpath}"
+    INSTALL_RPATH_USE_LINK_PATH   OFF)
+message(STATUS "安装后 RPATH: ${_lc_install_rpath}")
+
 # ---------------------------------------------------------------------------
 if(LC_BUILD_TESTS)
     enable_testing()
     add_subdirectory(tests)
 endif()
+
+# ---------------------------------------------------------------------------
+# 安装与打包（CPack → .deb）
+# ---------------------------------------------------------------------------
+include(cmake/Packaging.cmake)