v0.4.2: Welcome screen, status ticker, notifications, text scaling, networking fixes

Welcome screen with staggered counters while backend bootstraps. Header status
ticker for new posts/messages/reactions/comments/connection changes. Notification
fallback chain (Tauri plugin → Web API → notify-rust). Responsive text scaling
(Small/Normal/Large, persisted). Diagnostics moved to popover with on-demand
connections. Share details lightbox with QR code. Connect string prefers external
address. Stale N1 fix (disconnected routes excluded). Replication handler actively
fetches posts+blobs from requester. Hole punch registers remote address for relay.
Replication semaphore (3 concurrent). Peer labels show truncated node ID.

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

Cargo.lock

@@ -2746,13 +2746,14 @@ dependencies = [
 
 [[package]]
 name = "itsgoin-desktop"
-version = "0.4.1"
+version = "0.4.2"
 dependencies = [
  "anyhow",
  "base64 0.22.1",
  "dirs 5.0.1",
  "hex",
  "itsgoin-core",
+ "notify-rust",
  "open",
  "serde",
  "serde_json",