feat: add multi-platform Docker build system for Linux, macOS, and Windows

Replace the single Ubuntu-based container build with a dedicated
Dockerfile, build script, and launcher for each target platform.

Infrastructure:
- Add .dockerignore to minimize Docker build context
- Add container/builder-linux.Dockerfile (Ubuntu 24.04, GCC, native build)
- Add container/builder-macos.Dockerfile (multi-stage: SDK fetcher + osxcross/Clang 18)
- Add container/builder-windows.Dockerfile (LLVM-MinGW 20240619, vcpkg)
- Add container/macos/sdk-fetcher.py (auto-fetch macOS SDK from Apple catalog)
- Add container/macos/osxcross-toolchain.cmake (auto-detecting CMake toolchain)
- Add container/macos/triplets/arm64-osx-cross.cmake
- Add container/macos/triplets/x64-osx-cross.cmake
- Remove container/builder-ubuntu.Dockerfile (replaced by per-platform Dockerfiles)
- Remove container/build-in-container.sh and container/build-wowee.sh (replaced)

Build scripts (run inside containers):
- Add container/build-linux.sh (tar copy, FidelityFX clone, cmake/ninja)
- Add container/build-macos.sh (arch detection, vcpkg triplet, cross-compile)
- Add container/build-windows.sh (Vulkan import lib via dlltool, cross-compile)

Launcher scripts (run on host):
- Add container/run-linux.sh, run-macos.sh, run-windows.sh (bash)
- Add container/run-linux.ps1, run-macos.ps1, run-windows.ps1 (PowerShell)

Documentation:
- Add container/README.md (quick start, options, file structure, troubleshooting)
- Add container/FLOW.md (comprehensive build flow for each platform)

CMake changes:
- Add macOS cross-compile support (VulkanHeaders, -undefined dynamic_lookup)
- Add LLVM-MinGW/Windows cross-compile support
- Detect osxcross toolchain and vcpkg triplets

Other:
- Update vcpkg.json with ffmpeg feature flags
- Update resources/wowee.rc version string

container/build-macos.sh

@@ -0,0 +1,83 @@
+#!/bin/bash
+# macOS cross-compile entrypoint — runs INSIDE the macos container.
+# Toolchain: osxcross + Apple Clang, target: arm64-apple-darwin (default) or
+#            x86_64-apple-darwin when MACOS_ARCH=x86_64.
+# Bind-mounts:
+#   /src  (ro) — project source
+#   /out  (rw) — host ./build/macos
+
+set -euo pipefail
+
+SRC=/src
+OUT=/out
+NPROC=$(nproc)
+
+# Arch selection: arm64 (Apple Silicon) is the default primary target.
+ARCH="${MACOS_ARCH:-arm64}"
+case "${ARCH}" in
+    arm64)   VCPKG_TRIPLET=arm64-osx-cross  ;;
+    x86_64)  VCPKG_TRIPLET=x64-osx-cross    ;;
+    *)  echo "ERROR: unsupported MACOS_ARCH '${ARCH}'. Use arm64 or x86_64." ; exit 1 ;;
+esac
+
+# Auto-detect darwin target from osxcross binaries (e.g. arm64-apple-darwin24.5).
+OSXCROSS_BIN=/opt/osxcross/target/bin
+TARGET=$(basename "$(ls "${OSXCROSS_BIN}/${ARCH}-apple-darwin"*-clang 2>/dev/null | head -1)" | sed 's/-clang$//')
+if [[ -z "${TARGET}" ]]; then
+    echo "ERROR: could not find osxcross ${ARCH} compiler in ${OSXCROSS_BIN}" >&2
+    exit 1
+fi
+echo "==> Detected osxcross target: ${TARGET}"
+
+echo "==> [macos/${ARCH}] Copying source tree..."
+mkdir -p /wowee-build-src
+tar -C "${SRC}" \
+    --exclude='./build' --exclude='./logs' --exclude='./cache' \
+    --exclude='./container' --exclude='./.git' \
+    --exclude='./Data/character' --exclude='./Data/creature' \
+    --exclude='./Data/db' --exclude='./Data/environment' \
+    --exclude='./Data/interface' --exclude='./Data/item' \
+    --exclude='./Data/misc' --exclude='./Data/sound' \
+    --exclude='./Data/spell' --exclude='./Data/terrain' \
+    --exclude='./Data/world' \
+    -cf - . | tar -C /wowee-build-src -xf -
+
+cd /wowee-build-src
+
+echo "==> [macos/${ARCH}] Fetching external SDKs (if needed)..."
+if [ ! -f extern/FidelityFX-FSR2/src/ffx-fsr2-api/ffx_fsr2.h ]; then
+    git clone --depth 1 \
+        https://github.com/GPUOpen-Effects/FidelityFX-FSR2.git \
+        extern/FidelityFX-FSR2 || echo "Warning: FSR2 clone failed"
+fi
+
+SDK_REPO="${WOWEE_FFX_SDK_REPO:-https://github.com/Kelsidavis/FidelityFX-SDK.git}"
+SDK_REF="${WOWEE_FFX_SDK_REF:-main}"
+if [ ! -f "extern/FidelityFX-SDK/sdk/include/FidelityFX/host/ffx_frameinterpolation.h" ]; then
+    git clone --depth 1 --branch "${SDK_REF}" "${SDK_REPO}" extern/FidelityFX-SDK \
+        || echo "Warning: FidelityFX-SDK clone failed"
+fi
+
+echo "==> [macos/${ARCH}] Configuring with CMake (Release, Ninja, osxcross ${TARGET})..."
+cmake -S . -B "${OUT}" \
+    -G Ninja \
+    -DCMAKE_BUILD_TYPE=Release \
+    -DCMAKE_SYSTEM_NAME=Darwin \
+    -DCMAKE_OSX_ARCHITECTURES="${ARCH}" \
+    -DCMAKE_OSX_DEPLOYMENT_TARGET="${MACOSX_DEPLOYMENT_TARGET:-13.0}" \
+    -DCMAKE_C_COMPILER="${OSXCROSS_BIN}/${TARGET}-clang" \
+    -DCMAKE_CXX_COMPILER="${OSXCROSS_BIN}/${TARGET}-clang++" \
+    -DCMAKE_AR="${OSXCROSS_BIN}/${TARGET}-ar" \
+    -DCMAKE_RANLIB="${OSXCROSS_BIN}/${TARGET}-ranlib" \
+    -DCMAKE_TOOLCHAIN_FILE="${VCPKG_ROOT}/scripts/buildsystems/vcpkg.cmake" \
+    -DVCPKG_TARGET_TRIPLET="${VCPKG_TRIPLET}" \
+    -DVCPKG_OVERLAY_TRIPLETS=/opt/vcpkg-triplets \
+    -DCMAKE_INTERPROCEDURAL_OPTIMIZATION=OFF \
+    -DWOWEE_ENABLE_ASAN=OFF
+
+echo "==> [macos/${ARCH}] Building with ${NPROC} cores..."
+cmake --build "${OUT}" --parallel "${NPROC}"
+
+echo ""
+echo "==> [macos/${ARCH}] Build complete. Artifacts in: ./build/macos/"
+echo "    Binary: ./build/macos/bin/wowee"