refactor: delete _tasksByResidence and per-residence task cache plumbing

All readers and writers gone after the previous commits. Single source
of truth = DataManager._allTasks; residence views derive via
getTasksForResidence(id). Net deletion across DataManager, APILayer,
DataManagerObservable, Kotlin TaskViewModel, and the now-unused
TaskViewModel test.

Closes gitea#2

composeApp/src/commonMain/kotlin/com/tt/honeyDue/data/DataManager.kt

@@ -62,8 +62,6 @@ object DataManager {
         private set
     var tasksCacheTime: Long = 0L
         private set
-    var tasksByResidenceCacheTime: MutableMap<Int, Long> = mutableMapOf()
-        private set
     var contractorsCacheTime: Long = 0L
         private set
     var documentsCacheTime: Long = 0L
@@ -138,8 +136,6 @@ object DataManager {
     private val _allTasks = MutableStateFlow<TaskColumnsResponse?>(null)
     val allTasks: StateFlow<TaskColumnsResponse?> = _allTasks.asStateFlow()
 
-    private val _tasksByResidence = MutableStateFlow<Map<Int, TaskColumnsResponse>>(emptyMap())
-    val tasksByResidence: StateFlow<Map<Int, TaskColumnsResponse>> = _tasksByResidence.asStateFlow()
 
     // ==================== DOCUMENTS ====================
 
@@ -414,7 +410,6 @@ object DataManager {
 
     fun removeResidence(residenceId: Int) {
         _residences.value = _residences.value.filter { it.id != residenceId }
-        _tasksByResidence.value = _tasksByResidence.value - residenceId
         _documentsByResidence.value = _documentsByResidence.value - residenceId
         _residenceSummaries.value = _residenceSummaries.value - residenceId
 
@@ -445,16 +440,10 @@ object DataManager {
         persistToDisk()
     }
 
-    fun setTasksForResidence(residenceId: Int, response: TaskColumnsResponse) {
-        _tasksByResidence.value = _tasksByResidence.value + (residenceId to response)
-        tasksByResidenceCacheTime[residenceId] = currentTimeMs()
-        persistToDisk()
-    }
-
     /**
-     * Filter cached allTasks by residence ID to avoid separate API call.
-     * Returns null if allTasks not cached.
-     * This enables client-side filtering when we already have all tasks loaded.
+     * Filter cached allTasks by residence ID. Single source of truth for
+     * residence-scoped kanban data; returns null when _allTasks is null
+     * (caller must hit the API to populate).
      */
     fun getTasksForResidence(residenceId: Int): TaskColumnsResponse? {
         val allTasksData = _allTasks.value ?: return null
@@ -544,15 +533,6 @@ object DataManager {
             _allTasks.value = current.copy(columns = newColumns)
         }
 
-        // Remove from all residence task caches
-        _tasksByResidence.value = _tasksByResidence.value.mapValues { (_, tasks) ->
-            val newColumns = tasks.columns.map { column ->
-                val filteredTasks = column.tasks.filter { it.id != taskId }
-                column.copy(tasks = filteredTasks, count = filteredTasks.size)
-            }
-            tasks.copy(columns = newColumns)
-        }
-
         // Refresh summary from updated kanban data (API no longer returns summaries for CRUD)
         refreshSummaryFromKanban()
         persistToDisk()
@@ -795,7 +775,6 @@ object DataManager {
         _totalSummary.value = null
         _residenceSummaries.value = emptyMap()
         _allTasks.value = null
-        _tasksByResidence.value = emptyMap()
         _documents.value = emptyList()
         _documentsByResidence.value = emptyMap()
         _contractors.value = emptyList()
@@ -826,7 +805,6 @@ object DataManager {
         residencesCacheTime = 0L
         myResidencesCacheTime = 0L
         tasksCacheTime = 0L
-        tasksByResidenceCacheTime.clear()
         contractorsCacheTime = 0L
         documentsCacheTime = 0L
         summaryCacheTime = 0L
@@ -848,7 +826,6 @@ object DataManager {
         _totalSummary.value = null
         _residenceSummaries.value = emptyMap()
         _allTasks.value = null
-        _tasksByResidence.value = emptyMap()
         _documents.value = emptyList()
         _documentsByResidence.value = emptyMap()
         _contractors.value = emptyList()
@@ -861,7 +838,6 @@ object DataManager {
         residencesCacheTime = 0L
         myResidencesCacheTime = 0L
         tasksCacheTime = 0L
-        tasksByResidenceCacheTime.clear()
         contractorsCacheTime = 0L
         documentsCacheTime = 0L
         summaryCacheTime = 0L

composeApp/src/commonMain/kotlin/com/tt/honeyDue/viewmodel/TaskViewModel.kt

@@ -17,9 +17,6 @@ class TaskViewModel : ViewModel() {
     private val _tasksState = MutableStateFlow<ApiResult<TaskColumnsResponse>>(ApiResult.Idle)
     val tasksState: StateFlow<ApiResult<TaskColumnsResponse>> = _tasksState
 
-    private val _tasksByResidenceState = MutableStateFlow<ApiResult<TaskColumnsResponse>>(ApiResult.Idle)
-    val tasksByResidenceState: StateFlow<ApiResult<TaskColumnsResponse>> = _tasksByResidenceState
-
     private val _taskAddNewCustomTaskState = MutableStateFlow<ApiResult<CustomTask>>(ApiResult.Idle)
     val taskAddNewCustomTaskState: StateFlow<ApiResult<CustomTask>> = _taskAddNewCustomTaskState
 
@@ -35,16 +32,6 @@ class TaskViewModel : ViewModel() {
         }
     }
 
-    fun loadTasksByResidence(residenceId: Int, forceRefresh: Boolean = false) {
-        viewModelScope.launch {
-            _tasksByResidenceState.value = ApiResult.Loading
-            _tasksByResidenceState.value = APILayer.getTasksByResidence(
-                residenceId = residenceId,
-                forceRefresh = forceRefresh
-            )
-        }
-    }
-
     fun createNewTask(request: TaskCreateRequest) {
         println("TaskViewModel: createNewTask called with $request")
         viewModelScope.launch {

composeApp/src/commonTest/kotlin/com/tt/honeyDue/data/DataManagerTaskCacheTest.kt

@@ -135,21 +135,6 @@ class DataManagerTaskCacheTest {
         assertEquals(null, DataManager.getTasksForResidence(100))
     }
 
-    /// Lockdown: updateTask must NOT touch `_tasksByResidence`. That cache
-    /// is being deleted in Phase 3; until then, updateTask must leave it
-    /// alone. If a future commit re-introduces the conditional write
-    /// branch this test catches it.
-    @Test
-    fun updateTask_doesNotMutate_tasksByResidence() {
-        val before = DataManager.tasksByResidence.value
-        DataManager.updateTask(sampleTask(id = 1, residenceId = 100, column = "upcoming_tasks"))
-        assertEquals(
-            before,
-            DataManager.tasksByResidence.value,
-            "updateTask must not write to _tasksByResidence — that cache is deprecated"
-        )
-    }
-
     private fun sampleTask(
         id: Int,
         residenceId: Int,

composeApp/src/commonTest/kotlin/com/tt/honeyDue/viewmodel/TaskViewModelTest.kt

@@ -18,15 +18,6 @@ class TaskViewModelTest {
         assertIs<ApiResult.Idle>(viewModel.tasksState.value)
     }
 
-    @Test
-    fun testInitialTasksByResidenceState() {
-        // Given
-        val viewModel = TaskViewModel()
-
-        // Then
-        assertIs<ApiResult.Idle>(viewModel.tasksByResidenceState.value)
-    }
-
     @Test
     fun testInitialAddNewCustomTaskState() {
         // Given