atproto-entryway's account pages are moving onto the PDS portal's look (epic atproto-crates#k58x), and its signup onto the PDS signup's behaviour. Make what they need public: page, page_with_head, notice, sign_up_handle_hint and sign_up_handle.
Two small extractions keep the PDS rendering byte for byte the same: identity_nav, the signed-in header for any (path, label) sections with a slot for extra sign-out form fields (the entryway's CSRF token), which nav now calls; and from_this_site, the Sec-Fetch-Site test that require_same_origin now calls, for a caller with its own error type.
Refs: atproto-crates#f6vt