# [BUG] Fix outdated Todoist task link

## Description
Fix outdated Todoist task link.

## Technical Context
- Affects: `internal/api/todoist.go` (URL construction) or stored `url` field in DB
- Todoist may have changed their URL scheme
- Current URLs may be returning 404 or redirecting incorrectly

## Test Strategy

### Unit Test (Red)
**File:** `internal/api/todoist_test.go`

```go
func TestBuildTaskURL(t *testing.T) {
    taskID := "123456789"
    url := BuildTaskURL(taskID)

    // Assert current Todoist URL format
    // Option A: https://todoist.com/showTask?id=123456789
    // Option B: https://todoist.com/app/task/123456789
    assert.Equal(t, "https://todoist.com/app/task/123456789", url)
}
```

## Proposed Approach

1. Research current Todoist web URL format:
   - Check Todoist docs or inspect working links in browser
   - Likely format: `https://todoist.com/app/task/{task_id}` or `https://todoist.com/showTask?id={task_id}`
2. Update URL builder in `internal/api/todoist.go`
3. Consider migration for existing cached URLs in database:
   - Option A: Update on read (lazy migration)
   - Option B: Run migration script to update all stored URLs
4. If URL comes from API response directly, verify we're using the correct field

## Debugging Steps
1. Find a task ID in the database
2. Try current URL format in browser
3. Try alternative formats to find working one
4. Check Todoist API response for canonical URL field

## Affected Components
- `internal/api/todoist.go`
- `internal/api/todoist_test.go`
- Potentially `internal/store/sqlite.go` (if migration needed)

## Definition of Done
- [ ] Task links open correct Todoist page
- [ ] URL builder uses current format
- [ ] Existing cached URLs updated or migrated
- [ ] Unit test validates URL format