feat: Add admin-only protection to ebook operations

- Update ebook handlers to require admin role for CRUD operations
- Modify folder operations to be admin-only
- Update ebook scanner to associate books with admin who added them
- Add admin ID tracking to CreateEbook operations
- Restrict scanner operations to admin users only

internal/services/ebook_scanner.go

@@ -36,6 +36,7 @@ type EbookScanner struct {
 	db      *database.Queries
 	watcher *fsnotify.Watcher
 	folders []string
+	adminID pgtype.UUID
 }
 
 func NewEbookScanner(db *database.Queries) *EbookScanner {
@@ -50,6 +51,10 @@ func NewEbookScanner(db *database.Queries) *EbookScanner {
 	}
 }
 
+func (s *EbookScanner) SetAdminID(adminID pgtype.UUID) {
+	s.adminID = adminID
+}
+
 func (s *EbookScanner) SetFolders(folders []string) error {
 	s.folders = folders
 
@@ -291,6 +296,7 @@ func (s *EbookScanner) processEbookFile(ctx context.Context, path string) error
 		DatePublished:  pgtype.Date{Time: metadata.PublishDate, Valid: !metadata.PublishDate.IsZero()},
 		Contributors:   pgtype.Text{String: metadata.Contributors, Valid: metadata.Contributors != ""},
 		Tags:           pgtype.Text{String: metadata.Tags, Valid: metadata.Tags != ""},
+		AddedByAdminID: s.adminID,
 	})
 
 	return err