Fix service probes: correct endpoints and permissive HTTP module

- Workers: use http_internal module (HTTP/1.0 SimpleHTTPServer)
- ERPNext: use /api/method/ping, accept 401/403 (still means alive)
- Listmonk: use /health not /api/health (403 without auth)
- Forgejo: port 3000 not 3030
- Dev API: probe via HTTPS public URL (blackbox can't reach Docker)
- Added http_internal blackbox module accepting HTTP/1.0 + 401/403

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

monitoring/blackbox.yml

@@ -10,6 +10,16 @@ modules:
       tls_config:
         insecure_skip_verify: false
 
+  # Permissive module for internal services (Python SimpleHTTPServer, etc.)
+  http_internal:
+    prober: http
+    timeout: 10s
+    http:
+      valid_http_versions: ["HTTP/1.0", "HTTP/1.1", "HTTP/2.0"]
+      valid_status_codes: [200, 301, 302, 401, 403]
+      follow_redirects: false
+      preferred_ip_protocol: ip4
+
   tcp_connect:
     prober: tcp
     timeout: 5s