chore(release): v0.5.3 — rapikan dokumentasi, CI, dan workflow rilis

- bump versi 0.5.3 (version.txt, package.json)
- CHANGELOG: catatan 0.5.3 + arsip 0.5.2
- README: tautan Gitea/Forgejo baru, badge versi, bagian screenshot, fitur baru
- docs/RELEASE_NOTES_v0.5.3.md
- workflow CI (syntax + unit test) dan Release (buat rilis + asset zip) untuk Gitea & Forgejo

package.json

@@ -1,7 +1,7 @@
 {
   "name": "open-isp",
-  "version": "0.5.2",
-  "description": "OPEN-ISP — sistem billing & manajemen ISP open-source (PWA pelanggan, multi-OLT, RADIUS, WhatsApp, QRIS)",
+  "version": "0.5.3",
+  "description": "OPEN-ISP \u2014 sistem billing & manajemen ISP open-source (PWA pelanggan, multi-OLT, RADIUS, WhatsApp, QRIS)",
   "main": "app-customer.js",
   "scripts": {
     "start": "node app-customer.js",