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/tauri-app/gen/schemas/capabilities.json

@@ -1 +1 @@
-{"default":{"identifier":"default","description":"Default capability for the main window","local":true,"windows":["main"],"permissions":["core:default"]}}
+{"default":{"identifier":"default","description":"Default capability for the main window","local":true,"windows":["main"],"permissions":["core:default","notification:default","notification:allow-is-permission-granted","notification:allow-request-permission","notification:allow-notify","notification:allow-check-permissions","notification:allow-show"]}}