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>

stubs/include/Standard_Version.hxx

@@ -0,0 +1,23 @@
+/*
+ * KiCad Wasm Port - OpenCASCADE Standard_Version stub
+ *
+ * Provides stub version macros when OCC is disabled.
+ */
+
+#ifndef _Standard_Version_HeaderFile
+#define _Standard_Version_HeaderFile
+
+// Stub version when OCC is disabled
+#define OCC_VERSION_MAJOR 0
+#define OCC_VERSION_MINOR 0
+#define OCC_VERSION_MAINTENANCE 0
+#define OCC_VERSION_DEVELOPMENT "N/A"
+
+#define OCC_VERSION_STRING "0.0.0"
+#define OCC_VERSION_STRING_EXT "0.0.0 (disabled)"
+#define OCC_VERSION_COMPLETE "disabled"
+
+#define OCC_VERSION 0
+#define OCC_VERSION_HEX 0x000000
+
+#endif // _Standard_Version_HeaderFile