Butt your enclosure right up against the lock body, then you reduce shearing forces trying to pull it off the door. Extend the pull bar through your enclosure so you still have a manual override.
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Personally I love sho-goo. It holds great. And is also removable if needed. (Twist hard and it will come off then you can peel the stuff off). Stays flexible when cured and just use tape to get it to stay while curing
While I'm not adverse to home automation, is this something you need in your life, or just want? I like my perimeter security too be simple and tight, extra complications make the security audit much harder.
Will your insurance stand up to home made remote control unlocking?
To answer your question, place the servo in a suitably large enclosure and practically any adhesive should work, e.g. 3mM command strips or even velcro or double sided sticky. When confident that this is what you want, use a screw.