Add scan concurrency and login delay sliders

Serialised logins now sleep `login_delay` seconds between each SSH
auth to prevent AD/LDAP lockout. Both max sessions (1-10) and login
delay (0-15s) are configurable via UI sliders in the header and
passed as JSON to all scan endpoints.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ssh_client.py

@@ -2,7 +2,9 @@
 import re
 import logging
 import threading
+import time
 from concurrent.futures import ThreadPoolExecutor, as_completed
+from functools import partial
 from netmiko import ConnectHandler, NetmikoTimeoutException, NetmikoAuthenticationException
 from config import SSH_USERNAME, SSH_PASSWORD, SSH_PORT, SSH_TIMEOUT, DEVICE_TYPE
 from parser import (parse_lldp_neighbors, parse_mgmt_ip_from_interfaces,
@@ -15,7 +17,7 @@ logger = logging.getLogger(__name__)
 _login_lock = threading.Semaphore(1)
 
 
-def connect_and_query(ip):
+def connect_and_query(ip, login_delay=3):
     device = {
         "device_type":        DEVICE_TYPE,
         "host":               ip,
@@ -43,6 +45,8 @@ def connect_and_query(ip):
         with _login_lock:
             conn = ConnectHandler(**device)
             _pt.Transport._preferred_keys = _orig_preferred_keys
+            if login_delay > 0:
+                time.sleep(login_delay)
 
         try:
             hostname = conn.find_prompt().replace('#', '').replace('>', '').strip()
@@ -175,13 +179,14 @@ def _aruba_firmware(version_output):
 
 # ── Scan orchestration ────────────────────────────────────────────────────────
 
-def scan_all_switches(ip_list, progress_callback=None, max_workers=5):
+def scan_all_switches(ip_list, progress_callback=None, max_workers=5, login_delay=3):
     results = []
     total = len(ip_list)
     done  = 0
 
+    _scan = partial(connect_and_query, login_delay=login_delay)
     with ThreadPoolExecutor(max_workers=max_workers) as executor:
-        future_to_ip = {executor.submit(connect_and_query, ip): ip for ip in ip_list}
+        future_to_ip = {executor.submit(_scan, ip): ip for ip in ip_list}
 
         for future in as_completed(future_to_ip):
             ip = future_to_ip[future]
@@ -189,7 +194,7 @@ def scan_all_switches(ip_list, progress_callback=None, max_workers=5):
                 result = future.result()
             except Exception as e:
                 result = {"success": False, "ip": ip, "error": str(e)}
-            import time; time.sleep(2)  # avoid RADIUS lockout
+            time.sleep(2)  # avoid RADIUS lockout between result processing
 
             results.append(result)
             done += 1