implement one click update,sync option

src/ui/reaper_app.py

@@ -173,7 +173,7 @@ class DiscoReaperCLI:
         finally:
             await self.engine.close_connections()
 
-    async def backup_messages(self):
+    async def backup_messages(self, force_overwrite=None, skip_found_prompt=False, auto_sync_existing=False):
         """Option 2: Backup Channels structure and all message history."""
         if not self.tokens_valid: return
         try:
@@ -200,6 +200,20 @@ class DiscoReaperCLI:
                 console.print("[yellow]No text/news channels found to backup.[/yellow]")
                 return
 
+            selected_channels = []
+            
+            if auto_sync_existing:
+                selected_channels = [
+                    c for c in eligible_channels 
+                    if (self.exporter.export_path / "message_backup" / f"{c.id}.json").exists()
+                ]
+                if not selected_channels:
+                    console.print("[yellow]No existing backups found to sync.[/yellow]")
+                    return
+                # In auto-sync mode, we always use sync (force_overwrite=False) and skip prompts
+                force_overwrite = False
+                skip_found_prompt = True
+            else:
                 console.print(f"\n[bold]Select Channels to Backup ({len(eligible_channels)} total):[/bold]")
                 
                 # Identify duplicate names to show categories for them
@@ -231,7 +245,6 @@ class DiscoReaperCLI:
                 if selection_input.upper() == "B":
                     return
                 
-            selected_channels = []
                 if selection_input.upper() == "A":
                     selected_channels = eligible_channels
                 else:
@@ -254,8 +267,9 @@ class DiscoReaperCLI:
                     any_found = True
                     break
             
+            if force_overwrite is None:
                 force_overwrite = False
-            if any_found:
+                if any_found and not skip_found_prompt:
                     console.print("\n[bold yellow]Existing backup(s) found for some selected channels.[/bold yellow]")
                     console.print("(Y) Update & Sync Backup")
                     console.print("(F) [bold red]Force Overwrite Backup[/bold red]")
@@ -304,10 +318,11 @@ class DiscoReaperCLI:
             await self.engine.close_connections()
 
     async def sync_backup(self):
-        """Option 3: Update & Sync Backup (Runs a full pass but overwrites where needed)."""
-        console.print("[yellow]Syncing backup... (Re-validating all data)[/yellow]")
+        """Option 3: Update & Sync Backup (Automated incremental sync for existing backups)."""
+        console.print("[yellow]Syncing backup... (Updating existing data)[/yellow]")
         await self.backup_server_profile()
-        await self.backup_messages()
+        # Automatically select and sync existing backups
+        await self.backup_messages(auto_sync_existing=True)
 
     async def edit_configuration(self):
         # reuse or implement simplified version of edit_configuration from app.py