Bump to v0.12.4 — polls, custom relay, UI polish

NIP-1068 polls: create and vote on polls inline in the feed.
Switch default relay to custom Go relay (relay2.veganostr.com).
Note action icons with tooltips, sidebar icon cleanup,
search dedup fix, thread indentation fix.

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Vega",
-  "version": "0.12.3",
+  "version": "0.12.4",
   "identifier": "com.hoornet.vega",
   "build": {
     "beforeDevCommand": "npm run dev",