improvement: duedate added for shipped cases. cases and tasks ui and ux updated accordingly.

backend/prisma/migrations/20260713140000_lab_case_due_date/migration.sql

@@ -0,0 +1,5 @@
+-- Expected due date for lab cases (set by clinic at send / editable until complete)
+
+ALTER TABLE "lab_cases" ADD COLUMN "dueDate" TIMESTAMP(3);
+
+CREATE INDEX "lab_cases_dueDate_idx" ON "lab_cases"("dueDate");

backend/prisma/schema.prisma

@@ -214,6 +214,7 @@ model LabCase {
   sortOrder                 Int
   destinationOrganizationId String?
   sentAt                    DateTime?
+  dueDate                   DateTime?
   isImportant               Boolean   @default(false)
 
   treatment       Treatment                @relation(fields: [treatmentId], references: [id], onDelete: Cascade)