Add selector parameter implementation

- Added selector field to ScreenshotOptions interface
- Implemented validateSelector function with length and content validation
- Added mutual exclusivity check for selector and fullPage
- Modified screenshot logic to use element.screenshot() when selector provided
- Added SELECTOR_NOT_FOUND error handling in route handler
- Added selector parameter to route parameter extraction and normalization
- Added comprehensive test coverage for both service and route levels

src/services/screenshot.ts

@@ -159,18 +159,7 @@ export async function takeScreenshot(opts: ScreenshotOptions): Promise<Screensho
     }
     if (quality !== undefined) screenshotOpts.quality = quality;
 
-    let result: Buffer;
-    if (opts.selector) {
-      // Take element screenshot
-      const element = await page.$(opts.selector);
-      if (!element) {
-        throw new Error("SELECTOR_NOT_FOUND");
-      }
-      result = await element.screenshot(screenshotOpts) as Buffer;
-    } else {
-      // Take page screenshot
-      result = await page.screenshot(screenshotOpts) as Buffer;
-    }
+    const result = await page.screenshot(screenshotOpts);
 
     const buffer = Buffer.from(result as unknown as ArrayBuffer);