Stage 6 of the page builder: admin UI at /admin/pages for managing
page layouts. Page list shows all 14 pages grouped by category.
Editor supports reorder (up/down), add, remove, duplicate, save,
and reset to defaults. DirtyGuard JS hook warns on unsaved changes.
ARIA live regions announce block operations for screen readers.
Also: regenerate admin icons (81 rules via mix task with @layer
wrapping), add gen_smtp dep for SMTP email adapter, add :key to
page renderer block loop for correct LiveView diffing.
1309 tests, 0 failures.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
