Autosave: immediately persist books.xml after editing a book

- Add unitAppEvents with NotifyBooksChanged callback
- main: register @SaveBooksNow and implement it
- book: call NotifyBooksChanged after dialog OK to autosave changes

src/book.pas

@@ -53,7 +53,7 @@ procedure SetPdfCoverGenerationEnabled(AEnabled: Boolean);
 
 implementation
 
-uses UnitBookDialog, Forms;
+uses UnitBookDialog, Forms, unitAppEvents;
 
 procedure TBook.OpenEditDialogAsync({%H-}Data: PtrInt);
 var
@@ -66,6 +66,8 @@ begin
     begin
       EnsureScaledToCoverSize;
       if Assigned(mCover) then mCover.Invalidate;
+      // Persist changes immediately
+      NotifyBooksChanged;
     end;
   finally
     dlg.Free;

src/main.pas

@@ -7,7 +7,7 @@ interface
 uses
   Classes, Sysutils, Fileutil, Forms, Controls, Graphics, Dialogs, ExtCtrls, LazFileUtils,
   Book, BookCollection, LCLIntf, LResources, StdCtrls, LCLType, IniFiles, unitSettingsDialog,
-  unitCoverWorker, unitStorageXML, unitMetadata, LazUTF8;
+  unitCoverWorker, unitStorageXML, unitMetadata, unitAppEvents, LazUTF8;
 
 
 type
@@ -52,6 +52,7 @@ type
     procedure LayoutTimerTick(Sender: TObject);
     procedure ApplyFilterAndLayout;
     function AppConfigPath: String;
+    procedure SaveBooksNow;
   public
     { public declarations }
   end;
@@ -93,6 +94,16 @@ begin
   Result := IncludeTrailingPathDelimiter(GetAppConfigDirUTF8(False)) + 'config.ini';
 end;
 
+procedure TForm1.SaveBooksNow;
+begin
+  try
+    if Assigned(bookList) then
+      SaveBooksXML(dataXmlPath, bookList);
+  except
+    // ignore save errors during runtime autosave
+  end;
+end;
+
 procedure TForm1.PanelBackgroundClick({%H-}Sender: TObject);
 begin
  ActiveControl:=PanelBackground;
@@ -549,6 +560,9 @@ begin
 
  bookList:=TBookCollection.Create;
 
+  // Register autosave callback for book edits
+  OnBooksChanged := @SaveBooksNow;
+
   // speed up startup: we skipped synchronous PDF generation during load
   SetPdfCoverGenerationEnabled(False);
   try

src/unitAppEvents.pas

@@ -0,0 +1,24 @@
+unit unitAppEvents;
+
+{$mode objfpc}{$H+}
+
+interface
+
+type
+  TNotifyProc = procedure;
+
+var
+  OnBooksChanged: TNotifyProc = nil;
+
+procedure NotifyBooksChanged;
+
+implementation
+
+procedure NotifyBooksChanged;
+begin
+  if Assigned(OnBooksChanged) then
+    OnBooksChanged();
+end;
+
+end.
+