Enable exceptions and pthreads atomics for KiCad WASM build

Build fixes:
- Enable C++ exceptions in wxWidgets (--enable-exceptions, -fexceptions)
  Required for KiCad's OnExceptionInMainLoop override in debug builds
- Add -matomics -mbulk-memory to all dependency builds for shared memory
  Required for pthreads support with Emscripten
- Fix docker/build.sh output copy path (pcbnew/ not bin/)
- Make workspace mount read-only in docker-compose.yml

Updated dependency scripts:
- build-freetype.sh, build-harfbuzz.sh, build-protobuf.sh
- build-zstd.sh, build-opencascade.sh, build-boost.sh
- build-pixman.sh, build-cairo.sh (meson cross-file)
- build-wxuniversal-wasm.sh, build-pcbnew.sh

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/deps/build-all-deps.sh

@@ -43,6 +43,7 @@ log_info "=== Phase 1: Header-only libraries ==="
 log_info "=== Phase 2: Basic compression/serialization ==="
 "${SCRIPT_DIR}/build-zstd.sh" ${CLEAN}
 "${SCRIPT_DIR}/build-protobuf.sh" ${CLEAN}
+"${SCRIPT_DIR}/build-boost.sh" ${CLEAN}
 
 # 3. Font rendering stack
 log_info "=== Phase 3: Font rendering ==="
@@ -54,6 +55,11 @@ log_info "=== Phase 4: Graphics libraries ==="
 "${SCRIPT_DIR}/build-pixman.sh" ${CLEAN}
 "${SCRIPT_DIR}/build-cairo.sh" ${CLEAN}
 
+# 4b. Stub headers (needed for KiCad compilation but functionality is stubbed)
+log_info "=== Phase 4b: Stub dependencies (headers only) ==="
+"${SCRIPT_DIR}/build-curl-headers.sh" ${CLEAN}
+"${SCRIPT_DIR}/build-libgit2-headers.sh" ${CLEAN}
+
 # 5. Optional heavy dependencies
 if [ $WITH_OCC -eq 1 ]; then
     log_info "=== Phase 5a: OpenCASCADE (3D/STEP support) ==="