Lay out view, auth, validate, and handlers under internal/web while keeping
the cmd/panel API unchanged; update roadmap and changelog for web-split closure.
Co-authored-by: Cursor <cursoragent@cursor.com>
Name the copyright holder, ship NOTICE with the image, serve the licence
from the panel footer on every page, and record the vendored htmx licence.
Co-authored-by: Cursor <cursoragent@cursor.com>