Parallelize nmap phase in webrunner node scanner

scan_masscan_nmap() and scan_geo_scout() were running nmap serially —
one host at a time with a 60s timeout, turning a 1h estimate into 24h+
for large scans.

Both modes now use ThreadPoolExecutor with 10 workers (configurable via
WEBRUNNER_NMAP_WORKERS env var). geo-scout uses an inner scan_one()
helper to batch nmap + probe_service() per host within the same future.

Also fixed probe_service() bytes format antipattern and removed dead
targets_arg variable from scan_nmap_only().

run_scan.yml converted from command: > folded scalar to command: argv:
list form to prevent argument splitting on space-containing values.

modules/webrunner/tasks/run_scan.yml

@@ -10,12 +10,18 @@
     mode: '0644'
 
 - name: Run scan on {{ node_name }} ({{ node_ip_count }} IPs, mode={{ scan_mode }})
-  command: >
-    python3 /root/webrunner/node_scanner.py
-    --mode {{ scan_mode }}
-    --ports {{ ports_str }}
-    --rate {{ masscan_rate }}
-    --node-name {{ node_name }}
+  command:
+    argv:
+      - python3
+      - /root/webrunner/node_scanner.py
+      - --mode
+      - "{{ scan_mode }}"
+      - --ports
+      - "{{ ports_str }}"
+      - --rate
+      - "{{ masscan_rate }}"
+      - --node-name
+      - "{{ node_name }}"
   args:
     chdir: /root/webrunner
   register: scan_output
@@ -25,13 +31,21 @@
   when: not (use_tor | default(false) | bool)
 
 - name: Run scan via Tor on {{ node_name }} ({{ node_ip_count }} IPs, mode={{ scan_mode }})
-  command: >
-    proxychains4 -f /etc/proxychains4.conf
-    python3 /root/webrunner/node_scanner.py
-    --mode {{ scan_mode }}
-    --ports {{ ports_str }}
-    --rate {{ masscan_rate }}
-    --node-name {{ node_name }}
+  command:
+    argv:
+      - proxychains4
+      - -f
+      - /etc/proxychains4.conf
+      - python3
+      - /root/webrunner/node_scanner.py
+      - --mode
+      - "{{ scan_mode }}"
+      - --ports
+      - "{{ ports_str }}"
+      - --rate
+      - "{{ masscan_rate }}"
+      - --node-name
+      - "{{ node_name }}"
   args:
     chdir: /root/webrunner
   register: scan_output