Add ASN blocking documentation and configuration guides

- Add manage/asnblocking.mdx documentation page covering ASN-based access control
  - Explains benefits of blocking by Autonomous System Number
  - Documents common ASNs (cloud providers, ISPs, VPN services, CDNs)
  - Provides configuration patterns for VPN/proxy blocking, datacenter filtering
  - Includes manual ASN entry support and ASN lookup resources

- Add self-host/advanced/enable-asnblocking.mdx setup guide
  - Documents GeoLite2-ASN database installation steps
  - Includes config.yml parameter (maxmind_asn_db_path)
  - Mirrors enable-geoblocking.mdx structure for consistency

- Update docs.json navigation
  - Add asnblocking to Access Control group (after geoblocking)
  - Add enable-asnblocking to Advanced Configuration section

- Update self-host/community-guides/geolite2automation.mdx
  - Add GeoLite2-ASN to GEOIPUPDATE_EDITION_IDS
  - Add maxmind_asn_path configuration example
  - Update text to reference both geoblocking and ASN blocking features

docs.json

@@ -81,6 +81,7 @@
                                     "manage/access-control/forwarded-headers",
                                     "manage/access-control/login-page",
                                     "manage/geoblocking",
+                                    "manage/asnblocking",
                                     "manage/access-control/mfa",
                                     "manage/access-control/password-rotation",
                                     "manage/access-control/session-length",
@@ -150,6 +151,7 @@
                                     "self-host/advanced/database-options",
                                     "self-host/advanced/integration-api",
                                     "self-host/advanced/enable-geoblocking",
+                                    "self-host/advanced/enable-asnblocking",
                                     "self-host/advanced/metrics",
                                     "self-host/telemetry"
                                 ]