feat: Restore manual scanner requests for testing

- Recreate Scan Ebooks request with optional folder_paths parameter
- Recreate Start Scanner request for real-time monitoring
- Recreate Stop Scanner request for monitoring control
- All scanner requests remain admin-only as intended
- Essential for testing ebook discovery and scanning functionality

bruno/scanner/Stop Scanner.bru

@@ -0,0 +1,10 @@
+meta {
+  name: Stop Scanner
+  type: http
+  seq: 3
+}
+
+post {
+  url: {{base_url}}/api/scanner/stop
+  auth: bearer
+}