Bump version to 6.25.3

New patch release covering the macOS build target added in the previous
commit. Updates APP_VERSION, APP_VER_PATCH, package.json, and adds a
CHANGELOG section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "drg-xmrig",
-  "version": "6.25.2",
+  "version": "6.25.3",
   "description": "DragonX RandomX (rx/dragonx) CPU miner",
   "main": "index.js",
   "directories": {