feat: Model Gallery Endpoint Refactor / Mutable Galleries Endpoints (#991)

refactor for model gallery endpoints - bundle up resources into a
struct, make galleries mutable with some crud endpoints. This is
groundwork required for making efficient use of the new scraper - while
that PR isn't _quite_ ready yet, the goal is to have more, individually
smaller gallery files. Therefore, rather than requiring a full localai
service restart, these new endpoints have been added to make life
easier.

- Adds endpoints to add, list and remove model galleries at runtime
- Adds these endpoints to the Insomnia config
- Minor fix: loading file urls follows symbolic links now

api/options/options.go

@@ -99,6 +99,7 @@ func WithStringGalleries(galls string) AppOption {
 	return func(o *Option) {
 		if galls == "" {
 			log.Debug().Msgf("no galleries to load")
+			o.Galleries = []gallery.Gallery{}
 			return
 		}
 		var galleries []gallery.Gallery