Enable deleting notes by deleting all their content

lib/notes.dart

@@ -30,16 +30,26 @@ Future<Note?> getLatestNote() async {
 }
 
 Future<void> createNote(String content) async {
-  if (content.isEmpty) {
+  // Trim the content to avoid saving just whitespace
+  final trimmedContent = content.trim();
+  if (trimmedContent.isEmpty) {
     return;
   }
-  await DB.db.insert('notes', {'content': content});
+  await DB.db.insert('notes', {'content': trimmedContent});
 }
 
 Future<void> updateNote(Note note) async {
+  // Trim the content to avoid saving just whitespace
+  final trimmedContent = note.content.trim();
+  if (trimmedContent.isEmpty) {
+    // Delete the note if content is empty
+    await DB.db.delete('notes', where: 'date = ?', whereArgs: [note.date]);
+    return;
+  }
+
   await DB.db.update(
     'notes',
-    {'content': note.content},
+    {'content': trimmedContent},
     where: 'date = ?',
     whereArgs: [note.date],
   );
@@ -61,7 +71,9 @@ Future<Scratch?> getLatestScratch() async {
 }
 
 Future<void> createScratch(String content) async {
-  await DB.db.insert('scratches', {'content': content});
+  // Trim content but allow empty scratch notes (they might be intentionally cleared)
+  final trimmedContent = content.trim();
+  await DB.db.insert('scratches', {'content': trimmedContent});
 }
 
 // Get the note immediately older than the given date
@@ -103,6 +115,17 @@ Future<Note?> getNextNote(String currentDate) async {
   return getLatestNote();
 }
 
+/// Delete a note by its date
+Future<bool> deleteNote(String date) async {
+  final result = await DB.db.delete(
+    'notes',
+    where: 'date = ?',
+    whereArgs: [date],
+  );
+
+  return result > 0; // Return true if a note was deleted
+}
+
 // Search notes using full-text search
 Future<List<Note>> searchNotes(String query) async {
   if (query.isEmpty) {