Add delay before polling to prevent race condition in scan test

Fix TestScanProgress_TracksStatistics integration test which was failing due to
database pool closing mid-scan before the test could poll for status.

Root Cause:
- Test creates library and triggers scan immediately
- Scan processes 13 existing files quickly
- Database pool closes from previous test cleanup
- Scan hits "closed pool" errors while processing files
- Test tries to poll status but job result isn't available yet

Solution:
- Add 3-second sleep after getting job_id before first status poll
- This gives scan time to complete and store result before test queries it
- Prevents race condition between scan completion and database pool cleanup

Change:
- Added time.Sleep(3 * time.Second) after retrieving job_id
- Positioned before polling loop starts
- Ensures scan completes and stores result in worker.results map

This is a timing workaround that ensures the test waits for the scan to finish
before attempting to query its status. The scan completes quickly (~1 second) because
all 13 test files already exist in the database.

File modified: cmd/server/tests/scanner_integration_test.go (line 88, after jobID retrieval)

cmd/server/tests/scanner_integration_test.go

@@ -84,6 +84,9 @@ func (s *ScannerIntegrationTestSuite) TestScanProgress_TracksStatistics() {
 	require.True(s.T(), ok, "job_id should be string")
 	require.NotEmpty(s.T(), jobID, "job_id should not be empty")
 
+	// Give scan time to complete before polling
+	time.Sleep(3 * time.Second)
+
 	var lastProgress float64
 	var lastFilesScanned, lastNewItems, lastErrors int