feat(journals): implement auto-save toggle and visual status

- Added 'auto_save' preference to journals store
- Added toggle and status indicators (Check/X/Loader) to JournalEntry_Header
- Implemented auto-save logic with debounce in Journal Entry view

src/lib/ae_journals/ae_journals_stores.ts

@@ -81,6 +81,7 @@ const journals_local_data_struct: key_val = {
         llm__frequency_penalty: 0.0,
         llm__presence_penalty: 0.0,
 
+        auto_save: false,
         edit: false,
         edit_kv: {}
     }