Complete Phase 1: Build KiCad with optional dependencies disabled

Add CMake override modules, stub implementations, and patches to build
KiCad without CURL, libgit2, OpenCASCADE, and ngspice dependencies.

- cmake/: Find modules that provide stub targets when deps disabled
- stubs/include/: Header stubs for curl, git2, ngspice, OCC
- stubs/src/: Implementation stubs for disabled features
- patches/: Consolidated patch for KiCad source modifications
- scripts/: Build helper scripts

Verified full native build on macOS with all optional deps disabled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmake/FindCURL.cmake

@@ -0,0 +1,34 @@
+#
+# KiCad Wasm Port - CURL Find Module Override
+#
+# When KICAD_USE_CURL=OFF, this module provides stub values
+# so the build can proceed without libcurl.
+#
+
+# Check if curl is disabled
+if(DEFINED KICAD_USE_CURL AND NOT KICAD_USE_CURL)
+    message(STATUS "CURL: DISABLED (KICAD_USE_CURL=OFF)")
+
+    # Set variables that KiCad expects
+    set(CURL_FOUND TRUE)
+    set(CURL_INCLUDE_DIRS "")
+    set(CURL_LIBRARIES "")
+    set(CURL_VERSION_STRING "stub")
+
+    # Create an imported target that does nothing
+    if(NOT TARGET CURL::libcurl)
+        add_library(CURL::libcurl INTERFACE IMPORTED)
+    endif()
+
+    return()
+endif()
+
+# Otherwise, use CMake's built-in FindCURL
+# Remove our path to avoid recursion
+list(REMOVE_ITEM CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")
+
+# Use built-in module
+include(${CMAKE_ROOT}/Modules/FindCURL.cmake)
+
+# Restore module path
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")