Update client models to handle numeric decimals from optimized API

Model type updates:
- Change decimal cost fields from String to Double for better type safety
- actualCost: String? → Double? (TaskCompletion, TaskCompletionCreateRequest)
- estimatedCost: String? → Double? (CustomTask, TaskCreateRequest, TaskDetail)
- purchasePrice: String? → Double? (Residence, ResidenceCreateRequest)

TaskDetail model fixes:
- Add missing residenceName, createdBy, createdByUsername fields
- Add missing intervalDays field to match backend response
- Remove actualCost and notes fields (not in backend TaskDetailSerializer)
- Ensure 100% compatibility with Django API TaskDetailSerializer

UI input/output conversions:
- EditTaskScreen: Convert Double to String for display, String to Double for API
- AddTaskDialog: Convert String input to Double for API requests
- CompleteTaskDialog: Convert String input to Double for API requests
- App.kt: Handle type conversions in navigation route parameters

Display improvements:
- TaskCard: Update preview data to use numeric literals (150.00 vs "150.00")
- Cost display already handles Double correctly with string interpolation

Benefits:
- Type-safe numeric handling throughout the app
- Smaller JSON payloads (numbers vs quoted strings)
- Better performance with direct numeric deserialization
- Aligns with REST API best practices
- 100% backend compatibility verified

Testing:
- All models now match backend serializer field types exactly
- Build successful with no errors
- Ready for integration with optimized Django API

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

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

composeApp/src/commonMain/kotlin/com/example/mycrib/App.kt

@@ -323,7 +323,7 @@ fun App(
                                 statusId = task.status?.id,
                                 statusName = task.status?.name,
                                 dueDate = task.dueDate,
-                                estimatedCost = task.estimatedCost,
+                                estimatedCost = task.estimatedCost?.toString(),
                                 createdAt = task.createdAt,
                                 updatedAt = task.updatedAt
                             )
@@ -481,7 +481,7 @@ fun App(
                                 statusId = task.status?.id,
                                 statusName = task.status?.name,
                                 dueDate = task.dueDate,
-                                estimatedCost = task.estimatedCost,
+                                estimatedCost = task.estimatedCost?.toString(),
                                 createdAt = task.createdAt,
                                 updatedAt = task.updatedAt
                             )
@@ -509,9 +509,7 @@ fun App(
                             TaskStatus(it, route.statusName ?: "", displayName = route.statusName ?: "")
                         },
                         dueDate = route.dueDate,
-                        estimatedCost = route.estimatedCost,
-                        actualCost = null,
-                        notes = null,
+                        estimatedCost = route.estimatedCost?.toDoubleOrNull(),
                         createdAt = route.createdAt,
                         updatedAt = route.updatedAt,
                         nextScheduledDate = null,