refactor: remove empty register() methods in Boot classes

These Boot classes use the event-driven $listens pattern where
registration happens in event handlers (onAdminPanel, onDomainResolving),
not in register(). The empty overrides served no purpose since the parent
ServiceProvider already provides the method.

Fixes #17

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

src/Mod/Hub/Boot.php

@@ -210,11 +210,6 @@ class Boot extends ServiceProvider implements AdminMenuProvider
         ];
     }
 
-    public function register(): void
-    {
-        //
-    }
-
     // -------------------------------------------------------------------------
     // Event-driven handlers
     // -------------------------------------------------------------------------

src/Website/Hub/Boot.php

@@ -58,11 +58,6 @@ class Boot extends ServiceProvider implements AdminMenuProvider
         }
     }
 
-    public function register(): void
-    {
-        //
-    }
-
     /**
      * Get domains for this website.
      *