Add custom interval days support for task frequency

- Add customIntervalDays field to Kotlin models (TaskResponse, TaskCreateRequest, TaskUpdateRequest)
- Update Android AddTaskDialog to show interval field only for "Custom" frequency
- Update Android EditTaskScreen for custom frequency support
- Update iOS TaskFormView for custom frequency support
- Fix preview data in TaskCard and TasksSection to include new field
- Add customIntervalDays to OnboardingFirstTaskView

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

composeApp/src/commonMain/kotlin/com/example/casera/data/DataManager.kt

@@ -351,6 +351,30 @@ object DataManager {
         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.
+     */
+    fun getTasksForResidence(residenceId: Int): TaskColumnsResponse? {
+        val allTasksData = _allTasks.value ?: return null
+
+        // Filter each column's tasks by residence ID
+        val filteredColumns = allTasksData.columns.map { column ->
+            column.copy(
+                tasks = column.tasks.filter { it.residenceId == residenceId },
+                count = column.tasks.count { it.residenceId == residenceId }
+            )
+        }
+
+        return TaskColumnsResponse(
+            columns = filteredColumns,
+            daysThreshold = allTasksData.daysThreshold,
+            residenceId = residenceId.toString(),
+            summary = null  // Summary is global; residence-specific not available client-side
+        )
+    }
+
     /**
      * Update a single task - moves it to the correct kanban column based on kanban_column field.
      * This is called after task completion, status change, etc.