Fix build errors and add Domain Fronting option to HTTPS listener

[nth347]

Summary

• Fix build error: pass missing username argument to TsAxScriptResolveHooks in tc_agents.go, and resolve
  server.SMALL_VERSION undefined by moving the constant reference to the correct connector package in main.go

make server-ext
[+] Created 'dist' directory
[*] Building adaptixserver...
[ERROR] Failed to build AdaptixServer:
# AdaptixServer/core/connector
core/connector/tc_agents.go:100:171: not enough arguments in call to tc.teamserver.TsAxScriptResolveHooks
        have (string, string, string, int, string, map[string]any)
        want (string, string, string, int, string, map[string]interface{}, string)

• Add Domain Fronting support to the HTTP listener: a new boolean option in the Create/Edit Listener dialog
  that, when enabled, allows a mismatch between the configured Host headers and the incoming request's Host header
  (bypassing the Host header validation check)

Changes

Build fix (88179a8)

• tc_agents.go: add missing username arg to TsAxScriptResolveHooks call
• main.go: import connector package and reference connector.SMALL_VERSION instead of the non-existent
  server.SMALL_VERSION

Domain Fronting (dd70e7c)

• pl_transport.go: add DomainFronting bool field (json:"domain_fronting") to TransportConfig; skip Host
  header validation when DomainFronting is true
• ax_config.axs: add "Domain Fronting" checkbox to the HTTP Headers panel in the listener UI, wired to the
  domain_fronting config key

Test plan

• make server-ext builds without errors
• Create an HTTPS listener with Domain Fronting disabled - requests with a non-matching Host header are
  rejected as before
• Create an HTTPS listener with Domain Fronting enabled - requests with any Host header are accepted