feat(dm): implement incremental delivery for direct messages

- Added `onMessage` callback to `NostrClient.listDirectMessages` to stream decrypted messages.
- Updated `NostrService.loadDirectMessages` to use the callback and trigger `applyDirectMessage` incrementally.
- Updated `ProfileModalController` to allow rendering updates during the initial load if the reason is `load-incremental`.
- Verified changes with existing tests and code review.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/ui/profileModalController.js

@@ -4970,7 +4970,10 @@ export class ProfileModalController {
   }
 
   handleDirectMessagesUpdated(detail = {}) {
-    if (this.activeMessagesRequest) {
+    if (
+      this.activeMessagesRequest &&
+      detail?.reason !== "load-incremental"
+    ) {
       return;
     }