feat(media): bundle VLC, lazy video player, fullscreen with seek continuity

- Bundle VLC via ir.mahozad.vlc-setup plugin (all plugins for network playback)
- BundledVlcDiscoverer (Win/Linux) and MacOsVlcDiscoverer for bundled VLC discovery
- Lazy player activation — no VLC calls during composition, only on play click
- Pre-init VLC on background thread at startup
- Video controls: seek slider, volume, mute, fullscreen (two-row layout, no clipping)
- Buffering indicator (CircularProgressIndicator) while loading
- ActiveMediaManager enforces single-player — pauses others when new video plays
- Fullscreen passes seek position so lightbox resumes from current playback point
- LightboxOverlay renders videos (DesktopVideoPlayer) or images (ZoomableImage)
- Gitignore downloaded VLC binaries (appResources/{linux,macos,windows}/)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/build.gradle.kts

@@ -4,6 +4,7 @@ plugins {
     alias(libs.plugins.jetbrainsKotlinJvm)
     alias(libs.plugins.composeMultiplatform)
     alias(libs.plugins.jetbrainsComposeCompiler)
+    id("ir.mahozad.vlc-setup") version "0.1.0"
 }
 
 sourceSets {
@@ -77,8 +78,10 @@ dependencies {
 compose.desktop {
     application {
         mainClass = "com.vitorpamplona.amethyst.desktop.MainKt"
+        jvmArgs += "--add-opens=java.base/java.nio=ALL-UNNAMED"
 
         nativeDistributions {
+            appResourcesRootDir.set(project.layout.projectDirectory.dir("src/jvmMain/appResources"))
             targetFormats(TargetFormat.Dmg, TargetFormat.Msi, TargetFormat.Deb)
 
             packageName = "Amethyst"
@@ -103,3 +106,12 @@ compose.desktop {
         }
     }
 }
+
+vlcSetup {
+    vlcVersion.set("3.0.21")
+    shouldCompressVlcFiles.set(true)
+    shouldIncludeAllVlcFiles.set(true)
+    pathToCopyVlcLinuxFilesTo.set(file("src/jvmMain/appResources/linux/vlc"))
+    pathToCopyVlcMacosFilesTo.set(file("src/jvmMain/appResources/macos/vlc"))
+    pathToCopyVlcWindowsFilesTo.set(file("src/jvmMain/appResources/windows/vlc"))
+}