feat: data layer HTTP — consume sqlite_api en vez de SQLite directo

Nuevo data_http.cpp que obtiene todos los datos del registry via HTTP
POST a sqlite_api (/api/databases/registry/query). Mismas queries SQL
que el data layer SQLite pero ejecutadas remotamente. cpp-httplib como
cliente HTTP, nlohmann/json para parsear respuestas.

CMakeLists.txt actualizado: incluye data_http.cpp, vendor/ en includes,
linkea pthreads (Linux) y ws2_32 (Windows) para sockets.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CMakeLists.txt

@@ -17,6 +17,7 @@ endif()
 add_imgui_app(registry_dashboard
     main.cpp
     data.cpp
+    data_http.cpp
     views.cpp
     ${CMAKE_SOURCE_DIR}/functions/viz/kpi_card.cpp
     ${CMAKE_SOURCE_DIR}/functions/viz/bar_chart.cpp
@@ -31,6 +32,18 @@ add_imgui_app(registry_dashboard
 
 target_include_directories(registry_dashboard PRIVATE
     ${CMAKE_CURRENT_SOURCE_DIR}
+    ${CMAKE_CURRENT_SOURCE_DIR}/vendor
 )
 
 target_link_libraries(registry_dashboard PRIVATE SQLite::SQLite3)
+
+# cpp-httplib needs threads on Linux
+if(UNIX)
+    find_package(Threads REQUIRED)
+    target_link_libraries(registry_dashboard PRIVATE Threads::Threads)
+endif()
+
+# On Windows cross-compile, link ws2_32 for sockets
+if(WIN32)
+    target_link_libraries(registry_dashboard PRIVATE ws2_32)
+endif()