Fix TaskCompletionCreateRequest to remove completion_date field

The completion_date field is automatically set by the backend (auto_now_add)
and should not be sent in the create request. Removed this field from
TaskCompletionCreateRequest to match the API expectations.

Backend TaskCompletion model sets completion_date automatically, so
clients should not provide it when creating a completion.

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

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

composeApp/src/commonMain/kotlin/com/example/mycrib/models/TaskCompletion.kt

@@ -42,10 +42,10 @@ data class TaskCompletionCreateRequest(
     @SerialName("completed_by_phone") val completedByPhone: String? = null,
     @SerialName("completed_by_email") val completedByEmail: String? = null,
     @SerialName("company_name") val companyName: String? = null,
-    @SerialName("completion_date") val completionDate: String,
     @SerialName("actual_cost") val actualCost: String? = null,
     val notes: String? = null,
     val rating: Int? = null
+    // Note: completion_date is set automatically by the backend
 )
 
 @Serializable