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/src/main/java/com/scarriffle/calendarr/ui/MainViewModel.kt

@@ -0,0 +1,79 @@
+package com.scarriffle.calendarr.ui
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.scarriffle.calendarr.data.CalendarRepository
+import com.scarriffle.calendarr.data.CredentialStore
+import com.scarriffle.calendarr.data.SettingsStore
+import com.scarriffle.calendarr.data.remote.ApiProvider
+import com.scarriffle.calendarr.domain.model.AppSettings
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+enum class AppRoute { SETUP, LOGIN, MAIN }
+
+@HiltViewModel
+class MainViewModel @Inject constructor(
+    private val credentialStore: CredentialStore,
+    private val settingsStore: SettingsStore,
+    private val repository: CalendarRepository,
+    private val apiProvider: ApiProvider,
+) : ViewModel() {
+
+    private val _route = MutableStateFlow(computeRoute())
+    val route: StateFlow<AppRoute> = _route.asStateFlow()
+
+    private val _settings = MutableStateFlow(settingsStore.loadSettings())
+    val settings: StateFlow<AppSettings> = _settings.asStateFlow()
+
+    val serverUrl: String get() = credentialStore.serverUrl ?: ""
+    val username: String get() = credentialStore.username ?: ""
+    val isAdmin: Boolean get() = credentialStore.isAdmin
+
+    init {
+        if (_route.value == AppRoute.MAIN) refreshSettings()
+    }
+
+    private fun computeRoute(): AppRoute = when {
+        !credentialStore.isConfigured -> AppRoute.SETUP
+        !credentialStore.isLoggedIn -> AppRoute.LOGIN
+        else -> AppRoute.MAIN
+    }
+
+    fun onServerConfigured() { _route.value = computeRoute() }
+
+    fun onLoggedIn() {
+        _route.value = AppRoute.MAIN
+        refreshSettings()
+    }
+
+    fun logout() {
+        credentialStore.clearToken()
+        _route.value = computeRoute()
+    }
+
+    fun switchServer() {
+        credentialStore.clearAll()
+        apiProvider.invalidate()
+        _route.value = computeRoute()
+    }
+
+    /** Pull appearance settings from the server, caching them locally. */
+    fun refreshSettings() {
+        viewModelScope.launch {
+            runCatching { repository.getSettings() }.onSuccess { s ->
+                settingsStore.saveSettings(s)
+                _settings.value = s
+            }
+        }
+    }
+
+    fun applyLocalSettings(s: AppSettings) {
+        settingsStore.saveSettings(s)
+        _settings.value = s
+    }
+}