You should be able to edit your post (the pencil icon next to the title) after you post it and move it to a different category if you want. I wouldn't worry too much as long as it seems vaguely appropriate, however. Lots of people read all categories, and the Discourse forum software in use here seems better at showing people more posts than traditional hierarchical/folder-based forum software that you may be used to.
Back to this issue: are all the devices you want integrated into Hubitat already? If so, what you want on Hubitat is an app to tie them together. ("App" is the Hubitat term for automations, accessible from the "Apps" menu item on the left side of the admin UI. This is not to be confused with the optional Hubitat mobile app.) There are several built-in apps for common tasks, and you can always create a custom automation with Rule Machine (or even a custom app with your own Groovy code) if needed. But I'd recommend starting with the built-in apps. For your case, Simple Automation Rules sounds like a good choice. You can choose the contact sensor and tell it to turn on the lights when the sensor reports that the door is open and turn them off when closed.
I would not get Alexa involved in this if at all possible. If you have devices that only work with Alexa and not Hubitat directly, then you might have to. Otherwise, with Hubitat, you'll leave the cloud out of the picture (so things will be faster and more reliable), plus Hubitat apps are far more powerful than Alexa Routines (which you'd need to do this with Alexa--and if you're familiar with Routines, I guess apps are that analog on Hubitat).
While we're on the subject of creating automations, Hubitat Safety Monitor or the Notifications app are two ways you could make use of that Ecolink FireFighter to get notified when it detects an alarm if you want.