feat(player): add embedded-mpv player for macOS as experimental feature

- Introduced tooling for building and staging the macOS `libmpv` runtime for IPTVnator's embedded MPV player.
- Added `build-macos-runtime.mjs` for building an LGPL-compatible runtime from source.
- Created `stage-macos-runtime.mjs` for staging the built runtime artifacts.
- Implemented validation for the packaged embedded MPV runtime in `electron-after-pack.cjs` and `embedded-mpv-macos.cjs`.
- Updated packaging scripts to ensure the embedded MPV runtime is correctly integrated and validated during the build process.
- Added README files to document the expected layout and usage for the embedded MPV runtime artifacts.

Entire-Checkpoint: c6e522b4276c

electron-builder.json

@@ -19,7 +19,9 @@
     "asarUnpack": [
         "**/better-sqlite3/**",
         "**/bindings/**",
-        "**/file-uri-to-path/**"
+        "**/file-uri-to-path/**",
+        "**/*.node",
+        "**/*.dylib"
     ],
     "extraMetadata": {
         "main": "electron-backend/main.js"
@@ -95,7 +97,7 @@
             ]
         ]
     },
-    "afterPack": "./tools/packaging/linux-after-pack.cjs",
+    "afterPack": "./tools/packaging/electron-after-pack.cjs",
     "snap": {
         "base": "core22",
         "confinement": "strict",