add screenshot capture module using desktopCapturer

surfsense_desktop/src/modules/autocomplete/screenshot.ts

@@ -0,0 +1,27 @@
+import { desktopCapturer, screen } from 'electron';
+
+/**
+ * Captures the primary display as a base64-encoded PNG data URL.
+ * Uses the display's actual size for full-resolution capture.
+ */
+export async function captureScreen(): Promise<string | null> {
+  try {
+    const primaryDisplay = screen.getPrimaryDisplay();
+    const { width, height } = primaryDisplay.size;
+
+    const sources = await desktopCapturer.getSources({
+      types: ['screen'],
+      thumbnailSize: { width, height },
+    });
+
+    if (!sources.length) {
+      console.error('[screenshot] No screen sources found');
+      return null;
+    }
+
+    return sources[0].thumbnail.toDataURL();
+  } catch (err) {
+    console.error('[screenshot] Failed to capture screen:', err);
+    return null;
+  }
+}