fix(config): prevent card text overflow; fix(onboarding): persist completion server-side

Cards/Grid:
- Add min-width:0 to .device-grid to prevent grid overflow
- Add max-width:100%, overflow:hidden, word-break:break-word to .device-card
- Add min-width:0 and overflow-wrap to .device-card__body
- Bump config.css cache-bust to v=2

Onboarding:
- Add GET/POST /pos/api/config/onboarding-status endpoints in config_bp.py
- onboarding.js now checks server first before showing wizard
- On finish, POSTs completion to server (tenant_config table)
- Falls back to localStorage for fast path and offline resilience
- Bump onboarding.js cache-bust to v=2 in catalog.html

pos/blueprints/config_bp.py

@@ -577,3 +577,34 @@ def update_whatsapp_config():
     conn.close()
 
     return jsonify({'message': 'WhatsApp configuration updated'})
+
+
+@config_bp.route('/onboarding-status', methods=['GET'])
+@require_auth('pos.view')
+def get_onboarding_status():
+    """Check if tenant onboarding wizard has been completed."""
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute("SELECT value FROM tenant_config WHERE key = 'onboarding_completed'")
+    row = cur.fetchone()
+    cur.close()
+    conn.close()
+    return jsonify({'completed': row[0] == 'true' if row else False})
+
+
+@config_bp.route('/onboarding-status', methods=['POST'])
+@require_auth('pos.view')
+def set_onboarding_status():
+    """Mark tenant onboarding wizard as completed."""
+    data = request.get_json() or {}
+    completed = 'true' if data.get('completed') else 'false'
+    conn = get_tenant_conn(g.tenant_id)
+    cur = conn.cursor()
+    cur.execute("""
+        INSERT INTO tenant_config (key, value) VALUES (%s, %s)
+        ON CONFLICT (key) DO UPDATE SET value = EXCLUDED.value
+    """, ('onboarding_completed', completed))
+    conn.commit()
+    cur.close()
+    conn.close()
+    return jsonify({'completed': completed == 'true'})