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/models/Residence.kt

@@ -25,7 +25,7 @@ data class Residence(
     @SerialName("year_built") val yearBuilt: Int?,
     val description: String?,
     @SerialName("purchase_date") val purchaseDate: String?,
-    @SerialName("purchase_price") val purchasePrice: String?,
+    @SerialName("purchase_price") val purchasePrice: Double?,
     @SerialName("is_primary") val isPrimary: Boolean = false,
     @SerialName("created_at") val createdAt: String,
     @SerialName("updated_at") val updatedAt: String
@@ -133,7 +133,7 @@ data class ResidenceWithTasks(
     @SerialName("year_built") val yearBuilt: Int?,
     val description: String?,
     @SerialName("purchase_date") val purchaseDate: String?,
-    @SerialName("purchase_price") val purchasePrice: String?,
+    @SerialName("purchase_price") val purchasePrice: Double?,
     @SerialName("is_primary") val isPrimary: Boolean,
     @SerialName("task_summary") val taskSummary: TaskSummary,
     val tasks: List<TaskDetail>,