Show success toast when a draft is saved

Adds a "Draft saved" success toast notification after successfully
saving a draft. This applies to both save-and-close (handleSaveDraft)
and save-without-closing (saveCurrentDraft) flows. Previously, only
errors were shown, leaving users without feedback on successful saves.

Closes #9926

https://claude.ai/code/session_0115DTKCRzRvkWgMUVcokJvD

src/view/com/composer/Composer.tsx

@@ -605,11 +605,15 @@ export const ComposePost = ({
       })
 
       onClose()
+      setTimeout(() => {
+        Toast.show(_(msg`Draft saved`), {type: 'success'})
+      }, 500)
     } catch (e) {
       logger.error('Failed to save draft', {error: e})
       setError(getDraftSaveError(e))
     }
   }, [
+    _,
     saveDraft,
     composerState,
     composerDispatch,
@@ -633,12 +637,14 @@ export const ComposePost = ({
         existingDraftId: composerState.draftId,
       })
       composerDispatch({type: 'mark_saved', draftId: result.draftId})
+      Toast.show(_(msg`Draft saved`), {type: 'success'})
       return {success: true}
     } catch (e) {
       setError(getDraftSaveError(e))
       return {success: false}
     }
   }, [
+    _,
     saveDraft,
     composerState,
     composerDispatch,