Migrate macOS player from JNA to JNI with output scaling and performance improvements

[kdroidFilter]

Summary

• JNA → JNI: Replace JNA native bridge with a thin C JNI bridge (jni_bridge.c) that uses JNI_OnLoad / RegisterNatives to bind Swift @_cdecl exports to Kotlin external declarations; library is loaded via System.load() from bundled resources
• Output scaling: Add setOutputSize() in Swift — recreates AVPlayerItemVideoOutput at the display surface dimensions, significantly reducing memory for high-resolution (4K+) video by decoding at render size instead of native resolution; MacVideoPlayerSurface reports its size via onSizeChanged with a 120 ms debounce
• KVO observer fix: Move timeControlStatus observer from the HLS-only path (setupHLSMonitoring) to setupVideoOutputAndPlayer so it covers all media types, not just HLS streams
• Serial frame dispatcher: Replace Mutex-based frame serialization with Dispatchers.Default.limitedParallelism(1) — more idiomatic and removes the need for withLock in hot paths
• Remove frame hash: Drop the redundant per-frame hash computation; the serial dispatcher already prevents processing duplicate frames
• URI path fix: checkExistsIfLocalFile now uses File() directly instead of URI.create(), supporting paths with spaces and non-ASCII characters (e.g. accented filenames)
• Build script: Update build.sh to compile jni_bridge.c with JNI headers (-I${JAVA_HOME}/include) and link the resulting .o into the dylib alongside the Swift source

Test plan

• Run mediaplayer/src/jvmMain/native/macos/build.sh and confirm libNativeVideoPlayer.dylib builds for both arm64 and x86_64
• Play a local file — verify video renders correctly
• Play an HLS stream — verify isPlaying / isLoading state transitions correctly (KVO fix)
• Play a 4K video — confirm memory usage is lower than before (output scaling)
• Resize the player window — confirm native layer re-scales output after debounce
• Open a file with spaces or accented characters in its name — no "File not found" error
• Seek, pause, and resume — no regressions