feat(03-03): Ticket service, category service, API routes, and 28 integration tests

- ticket-category-service.ts: createCategory, updateCategory, listCategories
- ticket-service.ts: createTicket (TKT-NNNN numbering), updateTicket, getTicket, listTickets, transitionTicketStatus (guard map), resolveTicket (idempotent)
- 5 ticket API routes: GET/POST /api/tickets, GET/PUT /api/tickets/[id], POST /api/tickets/[id]/status
- 2 category API routes: GET/POST /api/ticket-categories, PUT /api/ticket-categories/[id]
- 28 integration tests: lifecycle, transitions, deactivated category rejection, idempotent resolve, cross-tenant isolation

src/lib/services/ticket-category-service.ts

@@ -0,0 +1,121 @@
+/**
+ * TicketCategoryService — Admin-configurable ticket category CRUD.
+ *
+ * ARCHITECTURE:
+ * - Categories are tenant-scoped and admin-configurable
+ * - Default ISP categories are seeded at tenant creation (see tenant.ts)
+ * - Deactivated categories (isActive=false) cannot be used for new tickets
+ * - Soft-deactivation preserves category history on existing tickets
+ */
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type TenantPrismaClient = any;
+
+// ---------------------------------------------------------------------------
+// Input/output types
+// ---------------------------------------------------------------------------
+
+export interface CreateCategoryInput {
+  name: string;
+  description?: string;
+}
+
+export interface UpdateCategoryInput {
+  name?: string;
+  description?: string;
+  isActive?: boolean;
+}
+
+// ---------------------------------------------------------------------------
+// createCategory
+// ---------------------------------------------------------------------------
+
+/**
+ * Create a new ticket category for this tenant.
+ *
+ * @throws Error if name is blank or already exists in tenant
+ */
+export async function createCategory(
+  tenantPrisma: TenantPrismaClient,
+  tenantId: string,
+  input: CreateCategoryInput
+) {
+  const { name, description } = input;
+
+  if (!name || !name.trim()) {
+    throw new Error("Category name is required");
+  }
+
+  try {
+    return await tenantPrisma.ticketCategory.create({
+      data: {
+        tenantId,
+        name: name.trim(),
+        description: description?.trim() ?? null,
+      },
+    });
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err);
+    if (message.includes("Unique constraint") || message.includes("P2002")) {
+      throw new Error(`Category name "${name.trim()}" already exists`);
+    }
+    throw err;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// updateCategory
+// ---------------------------------------------------------------------------
+
+/**
+ * Update a category's name, description, or isActive flag.
+ * Used by admins to rename or deactivate categories.
+ *
+ * @throws Error if category not found
+ */
+export async function updateCategory(
+  tenantPrisma: TenantPrismaClient,
+  categoryId: string,
+  input: UpdateCategoryInput
+) {
+  const { name, description, isActive } = input;
+
+  const data: Record<string, unknown> = {};
+  if (name !== undefined) data.name = name.trim();
+  if (description !== undefined) data.description = description.trim() || null;
+  if (isActive !== undefined) data.isActive = isActive;
+
+  try {
+    return await tenantPrisma.ticketCategory.update({
+      where: { id: categoryId },
+      data,
+    });
+  } catch (err) {
+    const message = err instanceof Error ? err.message : String(err);
+    if (message.includes("Record to update not found") || message.includes("P2025")) {
+      throw new Error(`Category not found: ${categoryId}`);
+    }
+    throw err;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// listCategories
+// ---------------------------------------------------------------------------
+
+/**
+ * List all categories for this tenant.
+ *
+ * @param options.activeOnly - If true, only return isActive=true categories (default: false)
+ */
+export async function listCategories(
+  tenantPrisma: TenantPrismaClient,
+  options: { activeOnly?: boolean } = {}
+) {
+  const { activeOnly = false } = options;
+
+  return tenantPrisma.ticketCategory.findMany({
+    where: activeOnly ? { isActive: true } : undefined,
+    orderBy: { name: "asc" },
+  });
+}