Release 1.2.2 stable — consolidated v1.2.1.x cycle

Promote the v1.2.1.x beta cycle to stable: version markers bumped
from 1.2.1.4-beta to 1.2.2 across version.txt, AppImage/package.json,
flask_server.py (3 places) and the four UI labels in login,
proxmox-dashboard, storage-overview and release-notes-modal.

Replace AppImage/ProxMenux-1.2.1.4-beta.AppImage with
ProxMenux-1.2.2.AppImage and regenerate the .sha256 sidecar
(097e2344675d4b21f1dd18c531c956c299a6507fbc3d0c9695418063581ba2b0).
The new binary is verified on all 4 lab hosts (.50 / .55 / .89 /
1.10) — same sha, all services active, runtime version markers
report 1.2.2.

CHANGELOG["1.2.2"] in release-notes-modal.tsx consolidates every beta
in the 1.2.1.x line (12 added / 13 changed / 18 fixed), and
CURRENT_VERSION_FEATURES is rewritten with the four stable highlights:
Health Monitor Thresholds, granular dismiss control (per-event
duration + Active Suppressions panel), Apprise notification channel
parity, and LXC update detection.

AppImage/scripts/flask_server.py

@@ -10564,7 +10564,7 @@ def api_health():
     return jsonify({
         'status': 'healthy',
         'timestamp': datetime.now().isoformat(),
-        'version': '1.2.1.4-beta'
+        'version': '1.2.2'
     })
 
 # ─── User-configurable health thresholds ─────────────────────────────────────
@@ -11049,7 +11049,7 @@ def api_info():
     """Root endpoint with API information"""
     return jsonify({
         'name': 'ProxMenux Monitor API',
-        'version': '1.2.1.4-beta',
+        'version': '1.2.2',
         'endpoints': [
             '/api/system',
             '/api/system-info',
@@ -11798,7 +11798,7 @@ if __name__ == '__main__':
         try:
             import sqlite3
             from pathlib import Path
-            MONITOR_VERSION = '1.2.1.4-beta'
+            MONITOR_VERSION = '1.2.2'
             db_path = Path('/usr/local/share/proxmenux/health_monitor.db')
             if db_path.exists():
                 conn = sqlite3.connect(str(db_path), timeout=10)