[feature] proof of work scraper deterrence (#4043)

This adds a proof-of-work based scraper deterrence to GoToSocial's middleware stack on profile and status web pages. Heavily inspired by https://github.com/TecharoHQ/anubis, but massively stripped back for our own usecase.

Todo:
- ~~add configuration option so this is disabled by default~~
- ~~fix whatever weirdness is preventing this working with CSP (even in debug)~~
- ~~use our standard templating mechanism going through apiutil helper func~~
- ~~probably some absurdly small performance improvements to be made in pooling re-used hex encode / hash encode buffers~~ the web endpoints aren't as hot a path as API / ActivityPub, will leave as-is for now as it is already very minimal and well optimized
- ~~verify the cryptographic assumptions re: using a portion of token as challenge data~~ this isn't a serious application of cryptography, if it turns out to be a problem we'll fix it, but it definitely should not be easily possible to guess a SHA256 hash from the first 1/4 of it even if mathematically it might make it a bit easier
- ~~theme / make look nice??~~
- ~~add a spinner~~
- ~~add entry in example configuration~~
- ~~add documentation~~

Verification page originally based on https://github.com/LucienV1/powtect

Co-authored-by: tobi <tobi.smethurst@protonmail.com>
Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4043
Reviewed-by: tobi <tsmethurst@noreply.codeberg.org>
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

internal/web/web.go

@@ -99,12 +99,16 @@ func (m *Module) Route(r *router.Router, mi ...gin.HandlerFunc) {
 
 	// Handlers that serve profiles and statuses should use
 	// the SignatureCheck middleware, so that requests with
-	// content-type application/activity+json can be served
+	// content-type application/activity+json can be served,
+	// and (if enabled) the nollamas middleware, to protect
+	// against scraping by shitty LLM bullshit.
 	profileGroup := r.AttachGroup(profileGroupPath)
 	profileGroup.Use(mi...)
 	profileGroup.Use(middleware.SignatureCheck(m.isURIBlocked), middleware.CacheControl(middleware.CacheControlConfig{
 		Directives: []string{"no-store"},
 	}))
+	nollamas := middleware.NoLLaMas(m.processor.InstanceGetV1)
+	profileGroup.Use(nollamas)
 	profileGroup.Handle(http.MethodGet, "", m.profileGETHandler) // use empty path here since it's the base of the group
 	profileGroup.Handle(http.MethodGet, statusPath, m.threadGETHandler)