Add comprehensive test suite with CI workflow

- 211 tests across 15 files covering services (tracking, discovery,
  metadata, backup, credits, webhooks, settings, update-check, colors,
  person), utilities (config, cron, providers, title-theme), and TMDB
  image URL helpers
- `lib/test-preload.ts` + `bunfig.toml` wire up a global in-memory
  SQLite DB with migrations for all DB-backed tests
- `lib/test-utils.ts` provides `clearAllTables()` and seed helpers
  (insertUser, insertTitle, insertTvShow, insertMovieWatch, etc.)
- Export `getBackupSource`, `isKnownBackup`, `isValidBackupFilename`,
  `buildBackupCron`, `performUpdateCheck` internals for direct testing
- GitHub Actions workflow runs `bun test --coverage` on push/PR to main

lib/cron.test.ts

@@ -0,0 +1,72 @@
+import { describe, expect, mock, test } from "bun:test";
+
+mock.module("@/lib/services/availability", () => ({
+  refreshAvailability: async () => {},
+}));
+mock.module("@/lib/services/backup", () => ({
+  createBackup: async () => ({}),
+  ensureBackupDir: async () => {},
+  pruneBackups: async () => {},
+}));
+mock.module("@/lib/services/credits", () => ({
+  refreshCredits: async () => {},
+}));
+mock.module("@/lib/services/image-cache", () => ({
+  cacheEpisodeStills: async () => {},
+  cacheImagesForTitle: async () => {},
+  cacheProfilePhotos: async () => {},
+  cacheProviderLogos: async () => {},
+  imageCacheEnabled: () => false,
+}));
+mock.module("@/lib/services/metadata", () => ({
+  refreshRecommendations: async () => {},
+  refreshTitle: async () => {},
+  refreshTvChildren: async () => {},
+}));
+mock.module("@/lib/services/update-check", () => ({
+  performUpdateCheck: async () => ({}),
+}));
+mock.module("@/lib/tmdb/client", () => ({
+  getTvDetails: async () => ({}),
+}));
+
+import { buildBackupCron } from "./cron";
+
+describe("buildBackupCron", () => {
+  test("6h frequency", () => {
+    expect(buildBackupCron("6h", "02:00")).toBe("0 */6 * * *");
+  });
+
+  test("12h frequency", () => {
+    expect(buildBackupCron("12h", "02:00")).toBe("0 2,14 * * *");
+  });
+
+  test("1d frequency (default)", () => {
+    expect(buildBackupCron("1d", "03:30")).toBe("30 3 * * *");
+  });
+
+  test("7d frequency with day of week", () => {
+    expect(buildBackupCron("7d", "04:15", 3)).toBe("15 4 * * 3");
+  });
+
+  test("7d frequency defaults to Sunday (0)", () => {
+    expect(buildBackupCron("7d", "02:00")).toBe("0 2 * * 0");
+  });
+
+  test("defaults to 1d when called with no args", () => {
+    expect(buildBackupCron()).toBe("0 2 * * *");
+  });
+
+  test("handles invalid time gracefully", () => {
+    const result = buildBackupCron("1d", "invalid");
+    expect(result).toBe("0 2 * * *");
+  });
+
+  test("6h ignores hour from time, uses minute only", () => {
+    expect(buildBackupCron("6h", "14:45")).toBe("45 */6 * * *");
+  });
+
+  test("12h wraps hour correctly", () => {
+    expect(buildBackupCron("12h", "18:00")).toBe("0 18,6 * * *");
+  });
+});