feat(projects): add createProject service (manual, shared numbering)

Introduces CreateProjectSchema (Zod 4, NaN-guarded coercions), the
createProject() service function (atomic shared-number generation inside
a $transaction), getNextProjectNumber() preview helper, and two Vitest
tests that verify standalone project creation and distinct sequential
numbers. Routes are deferred to a subsequent task.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/__tests__/manual-create.test.ts

@@ -0,0 +1,42 @@
+import { describe, it, expect, afterEach } from "vitest";
+import prisma from "../config/database";
+import { createProject } from "../services/projects.service";
+
+const createdProjectIds: number[] = [];
+const createdOrderIds: number[] = [];
+
+afterEach(async () => {
+  for (const id of createdProjectIds)
+    await prisma.projects.deleteMany({ where: { id } });
+  for (const id of createdOrderIds)
+    await prisma.orders.deleteMany({ where: { id } });
+  createdProjectIds.length = 0;
+  createdOrderIds.length = 0;
+  await prisma.number_sequences.deleteMany({ where: { type: "shared" } });
+});
+
+describe("createProject (manual, standalone)", () => {
+  it("assigns a shared number and is not linked to an order", async () => {
+    const result = await createProject({
+      name: "Test projekt",
+      status: "aktivni",
+    });
+    expect("project_number" in result).toBe(true);
+    if (!("project_number" in result)) return;
+    createdProjectIds.push(result.id);
+    expect(typeof result.project_number).toBe("string");
+    expect(result.project_number!.length).toBeGreaterThan(0);
+    expect(result.order_id).toBeNull();
+  });
+
+  it("gives consecutive standalone projects distinct numbers", async () => {
+    const a = await createProject({ name: "Projekt A", status: "aktivni" });
+    const b = await createProject({ name: "Projekt B", status: "aktivni" });
+    if ("project_number" in a) createdProjectIds.push(a.id);
+    if ("project_number" in b) createdProjectIds.push(b.id);
+    expect("project_number" in a && "project_number" in b).toBe(true);
+    if ("project_number" in a && "project_number" in b) {
+      expect(a.project_number).not.toBe(b.project_number);
+    }
+  });
+});