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/utils/title-theme.test.ts

@@ -0,0 +1,99 @@
+import { describe, expect, test } from "bun:test";
+import { getTitleThemeStyle, hexToRelativeLuminance } from "./title-theme";
+
+describe("hexToRelativeLuminance", () => {
+  test("black has luminance ~0", () => {
+    expect(hexToRelativeLuminance("#000000")).toBeCloseTo(0, 4);
+  });
+
+  test("white has luminance ~1", () => {
+    expect(hexToRelativeLuminance("#ffffff")).toBeCloseTo(1, 4);
+  });
+
+  test("mid-range grey", () => {
+    const lum = hexToRelativeLuminance("#808080");
+    expect(lum).toBeGreaterThan(0.15);
+    expect(lum).toBeLessThan(0.25);
+  });
+
+  test("pure red", () => {
+    const lum = hexToRelativeLuminance("#ff0000");
+    expect(lum).toBeCloseTo(0.2126, 3);
+  });
+
+  test("pure green", () => {
+    const lum = hexToRelativeLuminance("#00ff00");
+    expect(lum).toBeCloseTo(0.7152, 3);
+  });
+
+  test("pure blue", () => {
+    const lum = hexToRelativeLuminance("#0000ff");
+    expect(lum).toBeCloseTo(0.0722, 3);
+  });
+});
+
+describe("getTitleThemeStyle", () => {
+  test("returns empty object for null palette", () => {
+    expect(getTitleThemeStyle(null)).toEqual({});
+  });
+
+  test("returns empty object when vibrant is null", () => {
+    expect(
+      getTitleThemeStyle({
+        vibrant: null,
+        darkVibrant: "#123456",
+        lightVibrant: null,
+        muted: null,
+        darkMuted: null,
+        lightMuted: null,
+      }),
+    ).toEqual({});
+  });
+
+  test("dark color produces light foreground", () => {
+    const style = getTitleThemeStyle({
+      vibrant: "#1a1a2e",
+      darkVibrant: null,
+      lightVibrant: null,
+      muted: null,
+      darkMuted: null,
+      lightMuted: null,
+    });
+    expect(style["--primary" as keyof typeof style]).toBe("#1a1a2e");
+    expect(style["--primary-foreground" as keyof typeof style]).toBe(
+      "oklch(0.93 0.015 80)",
+    );
+  });
+
+  test("bright color produces dark foreground", () => {
+    const style = getTitleThemeStyle({
+      vibrant: "#ffff00",
+      darkVibrant: null,
+      lightVibrant: null,
+      muted: null,
+      darkMuted: null,
+      lightMuted: null,
+    });
+    expect(style["--primary" as keyof typeof style]).toBe("#ffff00");
+    expect(style["--primary-foreground" as keyof typeof style]).toBe(
+      "oklch(0.13 0.006 55)",
+    );
+  });
+
+  test("sets all expected CSS custom properties", () => {
+    const style = getTitleThemeStyle({
+      vibrant: "#e63946",
+      darkVibrant: null,
+      lightVibrant: null,
+      muted: null,
+      darkMuted: null,
+      lightMuted: null,
+    });
+    expect(style).toHaveProperty("--primary");
+    expect(style).toHaveProperty("--ring");
+    expect(style).toHaveProperty("--primary-foreground");
+    expect(style).toHaveProperty("--status-watching");
+    expect(style["--ring" as keyof typeof style]).toBe("#e63946");
+    expect(style["--status-watching" as keyof typeof style]).toBe("#e63946");
+  });
+});