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).

.github/workflows/build-apps.yml

@@ -11,7 +11,7 @@ on:
   push:
     branches: [develop, master]
 
-# Exposed to `expo prebuild` (app.config.js → extra.build) so Settings can show the
+# Exposed to `expo prebuild` (app.config.ts → extra.build) so Settings can show the
 # branch + commit + Actions run a CI build was made from. EAS cloud builds use
 # EAS_BUILD_* instead. The run number maps a sideloaded build back to its Actions
 # run (artifacts + logs) without needing Expo access.