httpd: serve apple-app-site-association for iOS universal links #310

The iOS app (krz/gitbay-ios#20) wants gitbay.org links opened in Safari to open in the app. That needs GET /.well-known/apple-app-site-association served as application/json with no redirect, listing the app ID and the paths the app can route.

• [web] apple_app_ids in the config; empty (the default) leaves the route unregistered, so the path 404s.
• Components cover owner, repo, issues, MRs, builds, tree/blob, commits, releases, wiki; exclude web-only paths (settings, login, admin, api, raw/archive/downloads, static, .well-known, forms).