refactor: improve worker type safety and scanner reliability

Worker improvements:
- Add strongly-typed result structs for all job types
- Replace map[string]interface{} with specific result types
- Add JSON tags to JobResult for proper API serialization
- Fix processJob to handle different result types correctly
- Improve directory scan job with proper library folder resolution
- Add debug logging for scan operations

Media scanner improvements:
- Add nil checks for database in GetPollInterval and GetAutoScanEnabled
- Fix pdfcpu API call signature (add validateOnly parameter)
- Add debug logging for scanDirectory with file counters
- Improve error handling and reporting

Test fixes:
- Fix default poll interval expectation from 30s to 60s
- Add settingsCache initialization to scanner tests
- Add folders initialization to ProcessDirtyDirectories test

internal/services/media_scanner.go

@@ -128,6 +128,10 @@ func (s *MediaScanner) GetPollInterval() time.Duration {
 		}
 	}
 
+	if s.db == nil {
+		return 60 * time.Second
+	}
+
 	// Cache miss - query database
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
@@ -154,6 +158,10 @@ func (s *MediaScanner) GetAutoScanEnabled() bool {
 		return strings.ToLower(cached) == "true"
 	}
 
+	if s.db == nil {
+		return true
+	}
+
 	// Cache miss - query database
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
@@ -1088,7 +1096,7 @@ func (s *MediaScanner) extractPDFMetadata(path string) (*MediaMetadata, error) {
 
 	// Use pdfcpu API to read PDF metadata
 	// Configuration: nil = default (lenient mode)
-	pdfInfo, err := pdfcpuapi.PDFInfo(f, filepath.Base(path), nil, nil)
+	pdfInfo, err := pdfcpuapi.PDFInfo(f, filepath.Base(path), nil, false, nil)
 	if err != nil {
 		fmt.Printf("Warning: failed to read PDF info from %s: %v\n", path, err)
 		// Fall back to filename as title
@@ -1863,6 +1871,9 @@ func (s *MediaScanner) waitForFileStability(filePath string) bool {
 }
 
 func (s *MediaScanner) scanDirectory(ctx context.Context, dirPath string) {
+	// Debug: Track file processing
+	filesSeen := 0
+	filesProcessed := 0
 	// Prevent concurrent scans of ANY directory
 	// Simple mutex is enough - job queue already serializes by directory
 	s.scan_mutex.Lock()
@@ -1903,7 +1914,7 @@ func (s *MediaScanner) scanDirectory(ctx context.Context, dirPath string) {
 		if !s.waitForFileStability(path) {
 			return nil
 		}
-
+		filesSeen++
 		relPath := strings.TrimPrefix(path, rootFolder+"/")
 		_, err = s.db.GetMediaItemByFilePath(ctx, database.GetMediaItemByFilePathParams{
 			FilePath:  relPath,
@@ -1917,10 +1928,14 @@ func (s *MediaScanner) scanDirectory(ctx context.Context, dirPath string) {
 				s.newItems++
 			}
 			s.totalFiles++
+			filesProcessed++
 		}
 
 		return nil
 	})
+	// Debug: Report scan results
+	fmt.Printf("DEBUG: scanDirectory of %s - filesSeen: %d, filesProcessed: %d, totalFiles: %d, newItems: %d, errors: %d\n",
+		dirPath, filesSeen, filesProcessed, s.totalFiles, s.newItems, s.errors)
 }
 
 // performInitialScan scans all root folders on startup