Have claude update the plan.

plan/future_improvements.md

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+# Future Improvements
+
+This document tracks architectural improvements and refactoring opportunities identified during development.
+
+## Architecture Refactoring
+
+### Repository + Service Pattern Migration
+
+**Current State**: Using Active Record pattern where TaskModel handles its own persistence and HTTP handlers contain business logic directly.
+
+**Future Improvement**: Migrate to Repository + Service pattern for better separation of concerns:
+
+```rust
+// Repository trait for data access abstraction
+trait TaskRepository {
+    async fn create(&self, task: &NewTask) -> Result<Task>;
+    async fn find_by_id(&self, id: Uuid) -> Result<Option<Task>>;
+    async fn update(&self, task: &Task) -> Result<Task>;
+    async fn delete(&self, id: Uuid) -> Result<()>;
+    async fn list_all(&self) -> Result<Vec<Task>>;
+}
+
+// Service layer for business logic
+struct TaskService {
+    repository: Box<dyn TaskRepository>,
+}
+
+impl TaskService {
+    async fn create_task(&self, title: String, description: Option<String>) -> Result<Task> {
+        // Input validation
+        // Business rules (e.g., auto-set completed_at when status changes)
+        // Call repository
+    }
+}
+```
+
+**Benefits**:
+- Better testability through repository mocking
+- Centralized business logic in service layer
+- Cleaner separation between data access, business logic, and HTTP handling
+- Easier to add complex business rules as the application grows
+
+**Implementation Plan**:
+1. Create TaskRepository trait and SqliteTaskRepository implementation
+2. Move database operations from TaskModel to repository
+3. Create TaskService with business logic
+4. Update HTTP handlers to use services instead of models directly
+5. Add comprehensive unit tests for service layer with mocked repositories
+
+**Priority**: Medium - Good for maintainability as the codebase grows, but current Active Record pattern works fine for MVP scope.