Bump to v0.12.3 — fix direct messages

NIP-17 gift-wrapped DMs were silently dropped by NDK's fetchEvents.
Switched to subscribe-based fetch that correctly receives kind 1059.

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Vega",
-  "version": "0.12.2",
+  "version": "0.12.3",
   "identifier": "com.hoornet.vega",
   "build": {
     "beforeDevCommand": "npm run dev",