tests: add coverage for src/actions/ (15 files) and src/lib/{admin,auth} (3 files)

- src/actions coverage: 2.4% -> 13.55%
- src/lib/admin coverage: 44.3% -> 84.81%
- src/lib/auth coverage: 90.52%
- vitest.config.ts: exclude .next.prev/ from test discovery

src/lib/admin/min-staff-rank.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it, vi } from "vitest";
+import { siteSettings } from "@/lib/services/site-settings";
+import { getMinStaffRank } from "./min-staff-rank";
+
+vi.mock("@/lib/services/site-settings", () => ({
+	siteSettings: { get: vi.fn() },
+}));
+
+describe("getMinStaffRank", () => {
+	it("returns numeric value", async () => {
+		vi.mocked(siteSettings.get).mockResolvedValue("7");
+		expect(await getMinStaffRank()).toBe(7);
+	});
+
+	it("uses fallback when setting missing", async () => {
+		vi.mocked(siteSettings.get).mockResolvedValue("");
+		expect(await getMinStaffRank(5)).toBe(5);
+	});
+
+	it("floors values", async () => {
+		vi.mocked(siteSettings.get).mockResolvedValue("7.8");
+		expect(await getMinStaffRank()).toBe(7);
+	});
+
+	it("rejects zero", async () => {
+		vi.mocked(siteSettings.get).mockResolvedValue("0");
+		expect(await getMinStaffRank(3)).toBe(3);
+	});
+});