Fix note sync reliability and Unicode filename support

- Fixed critical bug where notes with empty category had malformed IDs (leading slash)
- Added URL encoding for Czech and Unicode characters in WebDAV paths
- Fixed filename sanitization to preserve Unicode characters (only remove filesystem-unsafe chars)
- Updated note preview to show first non-empty line after title instead of repeating title
- Adjusted default column widths for better proportions (increased window width to 1300px)
- Protection mechanism now works correctly with proper note ID matching

src/services/syncManager.ts

@@ -10,6 +10,8 @@ export class SyncManager {
   private syncInProgress: boolean = false;
   private statusCallback: ((status: SyncStatus, pendingCount: number) => void) | null = null;
   private syncCompleteCallback: (() => void) | null = null;
+  private recentlyModifiedNotes: Set<number | string> = new Set();
+  private readonly PROTECTION_WINDOW_MS = 10000;
 
   constructor() {
     window.addEventListener('online', () => {
@@ -110,10 +112,13 @@ export class SyncManager {
         }
       }
       
-      // Remove deleted notes from cache
+      // Remove deleted notes from cache (but protect recently modified notes)
       for (const cachedNote of cachedNotes) {
         if (!serverMap.has(cachedNote.id)) {
-          await localDB.deleteNote(cachedNote.id);
+          // Don't delete notes that were recently created/updated (race condition protection)
+          if (!this.recentlyModifiedNotes.has(cachedNote.id)) {
+            await localDB.deleteNote(cachedNote.id);
+          }
         }
       }
       
@@ -236,6 +241,10 @@ export class SyncManager {
       this.notifyStatus('syncing', 0);
       const note = await this.api.createNoteWebDAV(title, content, category);
       await localDB.saveNote(note);
+      
+      // Protect this note from being deleted by background sync for a short window
+      this.protectNote(note.id);
+      
       this.notifyStatus('idle', 0);
       
       // Trigger background sync to fetch any other changes
@@ -297,8 +306,19 @@ export class SyncManager {
 
     try {
       this.notifyStatus('syncing', 0);
+      const oldId = note.id;
       const updatedNote = await this.api.updateNoteWebDAV(note);
+      
+      // If the note ID changed (due to filename change), delete the old cache entry
+      if (oldId !== updatedNote.id) {
+        await localDB.deleteNote(oldId);
+      }
+      
       await localDB.saveNote(updatedNote);
+      
+      // Protect this note from being deleted by background sync for a short window
+      this.protectNote(updatedNote.id);
+      
       this.notifyStatus('idle', 0);
       
       // Trigger background sync to fetch any other changes
@@ -349,6 +369,10 @@ export class SyncManager {
       const movedNote = await this.api.moveNoteWebDAV(note, newCategory);
       await localDB.deleteNote(note.id);
       await localDB.saveNote(movedNote);
+      
+      // Protect the moved note from being deleted by background sync
+      this.protectNote(movedNote.id);
+      
       this.notifyStatus('idle', 0);
       
       // Trigger background sync to fetch any other changes
@@ -370,6 +394,14 @@ export class SyncManager {
   getOnlineStatus(): boolean {
     return this.isOnline;
   }
+
+  // Protect a note from being deleted during background sync for a short window
+  private protectNote(noteId: number | string): void {
+    this.recentlyModifiedNotes.add(noteId);
+    setTimeout(() => {
+      this.recentlyModifiedNotes.delete(noteId);
+    }, this.PROTECTION_WINDOW_MS);
+  }
 }
 
 export const syncManager = new SyncManager();