feat(ui): storefront filters and admin category/tag management (#23)

Storefront gains a Filters drawer holding the category tree, colour-coded
tag pills, and a price range, with applied filters shown as removable
chips. Filter state lives in the URL query string, so a filtered view is
shareable and the back button works. Item cards now show their category
and tags.

Admin gains Categories and Tags tabs, and the item form gains a category
TreeSelect plus a tags Select that creates new tags on the fly.

The admin category tree tracks expansion in state rather than using
defaultExpandAll: that prop is evaluated once at mount, so a branch added
afterwards rendered collapsed and its children were unreachable. Creating
or moving a node now expands its parent. Caught by the new admin e2e spec.

The chip row is marked as a named group so its "Clear all" stays
distinguishable from the drawer's.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-08-17-categories-and-tags-design.md

@@ -169,9 +169,12 @@ described in `.claude/project-context.md` with no nginx change.
 - `GET|POST /api/admin/categories`, `PUT|DELETE /api/admin/categories/:id`
 - `GET|POST /api/admin/tags`, `PUT|DELETE /api/admin/tags/:id`
 
-`PUT /api/admin/categories/:id` accepts `name`, `parent_id`, and `sort_order`. Reparenting is
-validated against cycles server-side — a node may not become its own descendant — returning `400`.
-`DELETE` responds with the affected counts so the UI can confirm before committing.
+`GET /api/admin/categories` returns each node with an `item_count`, which is what lets the admin UI
+state the blast radius of a delete before calling it — the tree and the counts are already on the
+client, so no extra preview endpoint is needed. `PUT /api/admin/categories/:id` accepts `name`,
+`parent_id`, and `sort_order`; reparenting is validated against cycles server-side — a node may not
+become its own descendant — returning `400`. `DELETE` reports what it actually did, as
+`{ deleted_categories, uncategorized_items }`.
 
 `POST`/`PUT /api/admin/items` gain two multipart fields:
 
@@ -209,6 +212,9 @@ own line on mobile. The drawer enters from the right at every screen size (`plac
 near-full-width below the `md` breakpoint), with a sticky footer holding "Clear all" and
 "Show N items".
 
+The chip row is marked `role="group" aria-label="Active filters"`, which keeps its "Clear all"
+distinguishable from the identically-labelled control in the drawer.
+
 The tag section is labelled **"Tags — must have all"** so that selecting a second tag and watching
 the grid shrink reads as intentional rather than broken.
 
@@ -219,7 +225,9 @@ the grid shrink reads as intentional rather than broken.
 Two tabs added beside Inventory, Customers, and Settings:
 
 - **Categories** — antd `Tree` with drag-to-reparent, inline add/rename/delete, delete confirm
-  naming the affected subcategory and item counts
+  naming the affected subcategory and item counts. Expansion is controlled state rather than
+  `defaultExpandAll`: that prop is evaluated once at mount, so a branch created afterwards would
+  render collapsed and its children be unreachable. Creating or moving a node expands its parent.
 - **Tags** — list with rename, colour override from a palette, and delete showing the item count
 
 The item modal gains a category `TreeSelect` (with an explicit Uncategorized option) and a tags
@@ -249,8 +257,19 @@ user rule. Existing files keep their barrel imports — churning them is out of
 
 **E2E** (`frontend/tests/e2e/filters.spec.ts`)
 - Open the drawer, filter by category, tags, and price; assert the grid narrows
-- Remove a chip and assert the grid widens
+- A nested category is selectable, not just the roots
+- Remove a chip and assert the grid widens; "Clear all" resets everything
 - Reload a filtered URL and assert the filters are restored
+- Tags render on the item card
+
+**E2E** (`frontend/tests/e2e/admin-taxonomy.spec.ts`)
+- Create a category and a nested child, asserting the child stays visible
+- Create a tag and confirm a colour was assigned
+- The item form exposes category and tag fields
+
+Both e2e specs run against a database that is never reset between runs, so fixture names carry a
+per-run suffix, and `filters.spec.ts` treats re-entry into its `beforeAll` as a no-op — a worker can
+be handed the same spec file in more than one batch, and seeding twice would duplicate every item.
 
 ## Out of scope