Bootstrap Castarr from NodeCast prototype

Imported the native TV app (Kotlin, ExoPlayer, embedded remote server, QR
pairing) plus CONTEXT.md and ADRs 0001-0005. Rename, Compose for TV UI and
the Dispatcharr integration follow as tracked issues.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

build.gradle.kts

@@ -0,0 +1,4 @@
+plugins {
+    id("com.android.application") version "8.7.3" apply false
+    id("org.jetbrains.kotlin.android") version "2.0.21" apply false
+}