saves and mods on shared storage

[jspeyside]

Adds External storage support + Windows build support

External storage (save/mod accessibility)

• Request MANAGE_EXTERNAL_STORAGE / WRITE_EXTERNAL_STORAGE permissions on first launch
• On permission grant, migrate save data from private app storage to BanjoRecompiled/ in shared storage so saves and mods are accessible via file manager, survive app uninstalls, and can be cloud sync'd
• Add android:requestLegacyExternalStorage="true" for API 29 (Android 10) compatibility
• Bump versionCode 1 → 2 to allow over-the-air APK updates

Windows Android build support

• build.gradle: auto-detect Android SDK from LOCALAPPDATA when ANDROID_HOME is unset; normalize backslash paths; search name.exe/name.cmd extensions when checking PATH on Windows; validate NDK ld.lld using correct windows-x86_64 host arch
• CMakeLists.txt: use CMAKE_HOST_WIN32 (not WIN32) for host detection; resolve N64Recomp as an absolute path with platform-correct extension (N64Recomp.exe on Windows) so it is found without being on PATH; select dxc.exe for Windows hosts
• tools/setup_android_deps_windows.ps1: new script to cross-compile SDL2 and Freetype for Android from Windows; auto-detects SDK/NDK/CMake/Ninja, all paths driven by env vars with sensible defaults
• tools/prepare_generated_sources_windows.ps1: new script to build N64Recomp/RSPRecomp and generate runtime sources (RecompiledFuncs, patches, RSP) on Windows

Build hygiene

• Commit Gradle wrapper (gradlew, gradlew.bat, gradle/wrapper/) for reproducible builds without requiring Gradle pre-installed
• Add .gitattributes enforcing LF line endings for all text files (.bat/.cmd exempt); fixes CRLF warnings on Windows
• Add .idea/ to .gitignore
• Skip clang/ld.lld PATH validation in Gradle when patches/patches.bin already exists (the build step that needs them is skipped by CMake in that case)
• Generalize error messages that previously referenced a CI-specific user path

Feel free to edit or change!