Initial setup for navigation display with nav3

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

shared/src/androidMain/kotlin/net/newpipe/Constants.kt

@@ -0,0 +1,11 @@
+/*
+ * SPDX-FileCopyrightText: 2026 NewPipe e.V. <https://newpipe-ev.de>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package net.newpipe
+
+object Constants {
+
+    const val INTENT_SCREEN_KEY = "SCREEN"
+}

shared/src/androidMain/kotlin/net/newpipe/app/ComposeActivity.kt

@@ -9,6 +9,9 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import kotlinx.serialization.json.Json
+import net.newpipe.Constants
+import net.newpipe.app.navigation.Screen
 
 /**
  * Entry point for compose-related UI components on Android
@@ -19,7 +22,12 @@ class ComposeActivity : ComponentActivity() {
         super.onCreate(savedInstanceState)
 
         setContent {
-            App()
+            App(
+                // TODO: Change when everything is in compose and this is the primary activity
+                startDestination = Json.decodeFromString<Screen>(
+                    intent.getStringExtra(Constants.INTENT_SCREEN_KEY)!!
+                )
+            )
         }
     }
 }

shared/src/androidMain/kotlin/net/newpipe/app/extensions/Context.kt

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2026 NewPipe e.V. <https://newpipe-ev.de>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package net.newpipe.app.extensions
+
+import android.content.Context
+import android.content.Intent
+import kotlin.jvm.java
+import kotlinx.serialization.json.Json
+import net.newpipe.Constants
+import net.newpipe.app.ComposeActivity
+import net.newpipe.app.navigation.Screen
+
+/**
+ * Navigates to a given compose destination
+ */
+fun Context.navigateTo(screen: Screen) = Intent(this, ComposeActivity::class.java).also { intent ->
+    intent.putExtra(Constants.INTENT_SCREEN_KEY, Json.encodeToString(screen))
+    startActivity(intent)
+}