refactor: migrate app.config and Expo config plugins to TypeScript

Migrate the dynamic Expo config and all 12 local config plugins from
CommonJS .js to typed TypeScript:

- app.config.js -> app.config.ts (typed ConfigContext/ExpoConfig,
  behavior-identical port)
- plugins/*.js -> plugins/*.ts with `ConfigPlugin` typings from
  expo/config-plugins; plugin options are now type-checked (withGitPod)
- app.json plugin references updated to the .ts paths
- imports unified on expo/config-plugins (some plugins used the
  @expo/config-plugins alias)

Node evaluates the config at prebuild time and cannot parse TypeScript
plugin modules on its own (verified empirically: Expo transpiles
app.config.ts itself but not its imports), so the documented tsx
approach is used: `import "tsx/cjs"` at the top of app.config.ts plus
tsx as a devDependency.

Validation: resolved prebuild configs (expo config --type prebuild) are
byte-identical to the old JS config for both mobile and TV (modulo
plugin path extensions and the builtAt timestamp); full
`bun run prebuild` and `bun run prebuild:tv` pass and all Android
plugin mods are present in the generated project (media3 exclusions,
gradle properties, cast activity, network security config, alert
colors).

plugins/withAndroidManifest.ts

@@ -0,0 +1,46 @@
+import { type ConfigPlugin, withAndroidManifest } from "expo/config-plugins";
+
+const withGoogleCastAndroidManifest: ConfigPlugin = (config) =>
+  withAndroidManifest(config, async (mod) => {
+    const mainApplication = mod.modResults.manifest.application?.[0];
+
+    if (!mainApplication) {
+      return mod;
+    }
+
+    // Initialize activity array if it doesn't exist
+    if (!mainApplication.activity) {
+      mainApplication.activity = [];
+    }
+
+    const googleCastActivityExists = mainApplication.activity.some(
+      (activity) =>
+        activity.$?.["android:name"] ===
+        "com.reactnative.googlecast.RNGCExpandedControllerActivity",
+    );
+
+    // Only add the activity if it doesn't already exist
+    if (!googleCastActivityExists) {
+      mainApplication.activity.push({
+        $: {
+          "android:name":
+            "com.reactnative.googlecast.RNGCExpandedControllerActivity",
+          "android:theme": "@style/Theme.MaterialComponents.NoActionBar",
+          "android:launchMode": "singleTask",
+          "android:exported": "false",
+        },
+      });
+    }
+
+    const mainActivity = mainApplication.activity.find(
+      (activity) => activity.$?.["android:name"] === ".MainActivity",
+    );
+
+    if (mainActivity?.$) {
+      mainActivity.$["android:supportsPictureInPicture"] = "true";
+    }
+
+    return mod;
+  });
+
+export default withGoogleCastAndroidManifest;