feat: multi-day event bars, readiness-gated splash, top-bar spinner, 2-line titles, detail animation

- Month view now draws multi-day events as continuous bars (lane packing,
  per-week column span clipped at week boundaries, +N overflow) instead of a
  chip on every day; events bucketed per week once + memoized packing for
  smooth scrolling
- Startup: core-splashscreen covers the window from frame 0 (no warm-start
  flash); the in-app splash stays until the first events finish loading (loading
  starts behind the splash via an early-obtained CalendarViewModel + ready flow),
  so you no longer enter a laggy app
- Background load shows a small spinner in the top bar (removed the linear bar)
- Week/Day titles wrap to two smaller lines (no more truncation)
- Event detail opens with a slide+fade animation

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

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

@@ -3,12 +3,16 @@ package com.scarriffle.calendarr
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
+import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import com.scarriffle.calendarr.ui.CalendarrRoot
 import dagger.hilt.android.AndroidEntryPoint
 
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
+        // Covers the window from the first frame (no warm-start flash), then
+        // hands off to the in-app splash which stays until data is loaded.
+        installSplashScreen()
         super.onCreate(savedInstanceState)
         setContent {
             CalendarrRoot()