#17571 - Remove HTMX navigation

[bctiemann]

Closes: #17571

Removes experimental HTMX navigation.

Note: this leaves in place the {% formaction %} template tag as a hook for later customization, rather than removing all usages of it from templates.

Also does not remove existing non-experimental HTMX usages in forms, notifications, etc.

[pheus]

Drive‑by suggestion (not a reviewer/maintainer): In #20460 I added the docs for user preferences. Since this PR removes HTMX navigation, could we also remove it from the docs?

Source lines for reference:

netbox/docs/features/user-preferences.md

Lines 37 to 38 in 18a308a

	### HTMX navigation (experimental)
	Enables partial‑page navigation for supported views. Disable this preference if unexpected behavior is observed.

Happy to open a small docs PR if that helps. Thanks!

[bctiemann]

Nice catch, thanks! I've added that to this PR.

[jeremystretch]

I'm on the fence about retaining the formaction tag. While I see potential future benefit in keeping it in place, I worry that it'll only introduce confusion in the near term.

Approving this as-is; your call whether to keep it.

[bctiemann]

I'm going to go ahead and keep it as-is. We can remove it as tech debt later, meanwhile I think the comment is clear enough about the intent that a future dev ought not to be too confused.