fix: branded splash back, wider month range, December title bug

- Restore the branded in-app splash (Calendarr name + icon + © Scarriffle),
  held until the first events load; logo sized to match the system splash so it
  doesn't visibly jump, name/copyright fade in
- Month calendar now scrolls 10 years back / 50 years ahead (was ±18 months)
- Fix month/quarter title: use Month.getDisplayName instead of the 'LLLL'
  pattern, which dropped the month name (e.g. December showed only '2026')

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/com/scarriffle/calendarr/MainActivity.kt

@@ -4,35 +4,16 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
-import androidx.lifecycle.lifecycleScope
-import com.scarriffle.calendarr.data.CredentialStore
-import com.scarriffle.calendarr.data.StartupState
 import com.scarriffle.calendarr.ui.CalendarrRoot
 import dagger.hilt.android.AndroidEntryPoint
-import kotlinx.coroutines.delay
-import kotlinx.coroutines.launch
-import javax.inject.Inject
 
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
-
-    @Inject lateinit var startupState: StartupState
-    @Inject lateinit var credentialStore: CredentialStore
-
     override fun onCreate(savedInstanceState: Bundle?) {
-        // Single, uniform splash: keep the system splash on screen until the
-        // first events have loaded (or a timeout), so there is no two-stage
-        // splash and no entering a half-loaded, janky app.
-        val splash = installSplashScreen()
-        splash.setKeepOnScreenCondition { !startupState.ready.value }
-
+        // Covers the window from the first frame (incl. warm-start), then hands
+        // off to the in-app branded splash which stays until data is loaded.
+        installSplashScreen()
         super.onCreate(savedInstanceState)
-
-        // Nothing to load before login → reveal immediately.
-        if (!credentialStore.isLoggedIn) startupState.markReady()
-        // Safety timeout so the splash can never hang.
-        lifecycleScope.launch { delay(6000); startupState.markReady() }
-
         setContent {
             CalendarrRoot()
         }