add admin dashboard with setup checklist and stats

Dashboard at /admin shows setup progress (when not live), stat cards
(orders, revenue, products), and recent paid orders table. Replaces
the old AdminController redirect. Add Dashboard to sidebar nav as
first item, update admin bar and theme editor links to /admin.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PROGRESS.md

@@ -37,15 +37,14 @@ Plans: [admin-redesign.md](docs/plans/admin-redesign.md) | [setup-wizard.md](doc
 | ~~9~~ | ~~`Setup.setup_status/0` helper~~ | 2, 3 | 30m | done |
 | ~~10~~ | ~~ThemeHook gate (redirect to coming soon)~~ | 2, 8 | 30m | done |
 | ~~14~~ | ~~Go live / take offline toggle (on settings page)~~ | 2 | 30m | done |
-| | **Admin shell chain (priority)** | | | |
-| 1 | Filesystem restructure (consolidate live/ directories) | — | 2h | |
-| 6 | Admin shell component (sidebar nav, header) | 1 | 2-3h | |
-| 7 | Admin root + child layout templates | 1 | 1h | |
-| 11 | Theme editor back-to-admin link | 6 | 30m | |
-| 12 | Consolidate settings page | 6, 7 | 2-3h | |
+| ~~1~~ | ~~Filesystem restructure (consolidate live/ directories)~~ | — | 2h | done |
+| ~~6~~ | ~~Admin shell component (sidebar nav, header)~~ | 1 | 2-3h | done |
+| ~~7~~ | ~~Admin root + child layout templates~~ | 1 | 1h | done |
+| ~~11~~ | ~~Theme editor back-to-admin link~~ | 6 | 30m | done |
+| ~~4~~ | ~~Admin bar on shop pages~~ | — | 1h | done |
+| ~~12~~ | ~~Consolidate settings page~~ | 6, 7 | 2-3h | done |
+| | **Next up** | | | |
 | 13 | Admin dashboard (+ setup checklist) | 6, 7, 9 | 2h | |
-| | **Independent** | | | |
-| 4 | Admin bar on shop pages | — | 1h | |
 | 5 | Search (functional search with results) | — | 3-4h | |
 | | **Needs admin stable** | | | |
 | 15 | Setup wizard + admin tests | 13 | 1.5h | |