v0.3.4: Comment edit/delete, native notifications, forward-compatible protocol, UI fixes

Comment edit & delete:
- EditComment/DeleteComment BlobHeaderDiffOps with upstream+downstream propagation
- Trust-based: comment author can edit/delete, post author can delete
- Storage: edit_comment(), delete_comment() methods
- Frontend: inline edit (Enter/Escape), delete with confirm

Native notifications:
- tauri-plugin-notification for system notifications on all platforms
- Triggers for messages, new posts, reactions, and comments
- notif_reacts setting added, button-group toggles replace dropdowns
- _notifReady flag prevents startup spam

Protocol hardening:
- BlobHeaderDiffOp::Unknown variant with #[serde(other)] for forward compatibility
- Old nodes silently skip unknown ops instead of crashing

UI fixes:
- Self removed from Following list
- Offline follows in lightbox popup (auto-show if no one online)
- Sent DMs filtered from My Posts
- Comment threading scoped to closest .post (fixes duplicate ID issue)
- Select dropdown text legible in WebKitGTK (black on white options)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/core/src/connection.rs

@@ -5493,6 +5493,18 @@ impl ConnectionManager {
                         }
                         let _ = storage.store_comment(comment);
                     }
+                    BlobHeaderDiffOp::EditComment { author, post_id, timestamp_ms, new_content } => {
+                        // Trust-based: only the comment author can edit
+                        if *author == sender || sender == payload.author {
+                            let _ = storage.edit_comment(author, post_id, *timestamp_ms, new_content);
+                        }
+                    }
+                    BlobHeaderDiffOp::DeleteComment { author, post_id, timestamp_ms } => {
+                        // Trust-based: comment author or post author can delete
+                        if *author == sender || sender == payload.author {
+                            let _ = storage.delete_comment(author, post_id, *timestamp_ms);
+                        }
+                    }
                     BlobHeaderDiffOp::SetPolicy(new_policy) => {
                         if sender == payload.author {
                             let _ = storage.set_comment_policy(&payload.post_id, new_policy);
@@ -5504,6 +5516,7 @@ impl ConnectionManager {
                             parent_post_id: payload.post_id,
                         });
                     }
+                    BlobHeaderDiffOp::Unknown => {} // future ops — silently skip
                 }
             }
         }