feat: add darkMode and hideSelectors screenshot parameters

- darkMode: emulates prefers-color-scheme: dark before navigation
- hideSelectors: injects CSS to hide elements before capture
  - POST: accepts string or string array
  - GET: accepts comma-separated string
  - Validation: max 10 selectors, each max 200 chars
- OpenAPI docs updated for both GET and POST endpoints
- 13 new tests added (service + route)

src/services/screenshot.ts

@@ -14,6 +14,8 @@ export interface ScreenshotOptions {
   deviceScale?: number;
   delay?: number;
   waitUntil?: "load" | "domcontentloaded" | "networkidle0" | "networkidle2";
+  darkMode?: boolean;
+  hideSelectors?: string[];
 }
 
 export interface ScreenshotResult {
@@ -42,6 +44,10 @@ export async function takeScreenshot(opts: ScreenshotOptions): Promise<Screensho
   try {
     await page.setViewport({ width, height, deviceScaleFactor: deviceScale });
 
+    if (opts.darkMode) {
+      await page.emulateMediaFeatures([{ name: 'prefers-color-scheme', value: 'dark' }]);
+    }
+
     await Promise.race([
       (async () => {
         await page.goto(opts.url, { waitUntil, timeout: 20_000 });
@@ -53,6 +59,12 @@ export async function takeScreenshot(opts: ScreenshotOptions): Promise<Screensho
         if (opts.delay && opts.delay > 0) {
           await new Promise(r => setTimeout(r, Math.min(opts.delay!, 5000)));
         }
+
+        if (opts.hideSelectors && opts.hideSelectors.length > 0) {
+          await page.addStyleTag({
+            content: opts.hideSelectors.map(s => s + ' { display: none !important }').join('\n')
+          });
+        }
       })(),
       new Promise<never>((_, reject) => setTimeout(() => reject(new Error("SCREENSHOT_TIMEOUT")), TIMEOUT_MS)),
     ]);