feat: full Compose UI (auth, calendar, events, accounts, settings, profile)

- Root navigation (server setup -> login+2FA -> calendar) with settings-driven theme
- CalendarViewModel mirroring iOS CalendarStore: range-based caching,
  background prefetch, hidden/banished calendar filters, event CRUD
- Five calendar views: Month, Week, Day, Quarter, Agenda (shared time grid)
- Event detail + editor sheets (platform date/time pickers, color override,
  writable-calendar picker) across local/caldav/google/homeassistant
- Calendar filter sheet (per-calendar show/hide)
- Accounts screen: add/delete CalDAV, local, iCal, Home Assistant; list Google
- Settings: view/week-start/language/colors/contrast/hour-height/cache range,
  synced to server
- Profile: email, password change, 2FA enable/disable
- gradlew build (lint + tests + assemble) passes

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

app/build.gradle.kts

@@ -87,7 +87,7 @@ dependencies {
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3")
 
     testImplementation("junit:junit:4.13.2")
-    androidTestImplementation("androidx.test.ext:junit:1.1.6")
+    androidTestImplementation("androidx.test.ext:junit:1.1.5")
     androidTestImplementation("androidx.test.espresso:espresso-core:3.5.1")
     androidTestImplementation(platform("androidx.compose:compose-bom:2023.10.01"))
     androidTestImplementation("androidx.compose.ui:ui-test-junit4")