Add Sumly to an Android app

Set up Kotlin and Jetpack Compose for Sumly in this project.

Sumly (https://sumly.dev) shows revenue next to the visits and app users it came from. The full guide is https://sumly.dev/install/kotlin; read it if anything below is unclear.

Steps:
1. In Sumly, open Visitors and copy your project's public key (`sl_…`). Download https://sumly.dev/sdk/Sumly.kt into your app module (change its package line if you like). The app needs the INTERNET permission, which almost every app has.
2. In `Application.onCreate`, call `Sumly.init(this, siteKey = "sl_…")`. After `Purchases.configure`, and again after each `logIn` or `logOut`, call `Sumly.identify(Purchases.sharedInstance.appUserID)`.
3. Count screens: with Navigation Compose, a listener on the NavController names each screen as it opens; anywhere else, `Sumly.screen("Paywall")`.

Setup: In your Application class.
```
class MyApp : Application() {
    override fun onCreate() {
        super.onCreate()
        Sumly.init(this, siteKey = "sl_your_key")
        Purchases.configure(PurchasesConfiguration.Builder(this, "goog_…").build())
        Sumly.identify(Purchases.sharedInstance.appUserID)
    }
}

// after signing in or out
Purchases.sharedInstance.logInWith(user.id) { _, _ ->
    Sumly.identify(Purchases.sharedInstance.appUserID)
}
```

Compose screens: The listener gets the screen it is on as soon as it is added, then each new one.
```
val navController = rememberNavController()

DisposableEffect(navController) {
    val listener = NavController.OnDestinationChangedListener { _, destination, _ ->
        Sumly.screen(destination.route ?: "App")
    }
    navController.addOnDestinationChangedListener(listener)
    onDispose { navController.removeOnDestinationChangedListener(listener) }
}

// events
Sumly.track("trial_started", mapOf("plan" to "yearly"))
```

Consent: Where your app asks first.
```
Sumly.init(this, siteKey = "sl_your_key", waitForConsent = true)

Sumly.consent(true)    // when the person agrees
Sumly.consent(false)   // when they refuse, or take it back
```

Own domain: Optional: your own address takes app events too.
```
Sumly.init(this, siteKey = "sl_your_key", endpoint = "https://signal.example.com")
```

Keep in mind: With type-safe routes (Navigation 2.8 and later) a destination's route is the route class's name, which may be long; give `Sumly.screen` a shorter name of your own if you like. No advertising id. In Google Play's Data safety, declare app interactions, user ids and approximate location, collected for analytics. The queue is kept in SharedPreferences. With ACCESS_NETWORK_STATE it sends as soon as the network is back; without it, on its timer.

How to work:
- Look at how this project is built first, and fit the code to its framework and its way of doing things; the examples above are a starting point, not something to paste as is.
- Steps that happen in a dashboard (Sumly, or Kotlin and Jetpack Compose's own) are mine: tell me exactly what to click, then wait for me.
- Keys the code needs belong in environment variables, never in the code or the repository. Never ask me to paste a secret key into this chat; tell me which variable to set.
- Change only what this needs, show me the changes before you commit, and tell me how to check that it works.
- sl_your_key stands for the project's public key; it is on the Visitors page in Sumly. Ask me for it.