fix(admin): theme, American English, and inventory/reservation tooling (#27)

Seven reported items, of which the first four had two root causes.

The active tab was invisible in dark mode because colorPrimary was
hardcoded to #1a1a1a in both themes. The accent now inverts with the
theme, and colorTextLightSolid inverts with it, or a near-white accent
would get antd's default white label and disappear.

The Category tab, Tag tab, and item-form category selector ignored the
theme entirely. antd declares main: lib/index.js and module: es/index.js,
so importing from 'antd' resolves to the ES build while 'antd/lib/...'
loads the CommonJS one — two copies, two React contexts, and no
ConfigProvider for anything deep-imported. Switching those files to
antd/es/* keeps the deep-import convention and shares the instance. This
was introduced by my own use of the lib path; es is correct under Vite.
Two storefront components had the same latent bug.

"Colour" is now "Color".

The Customers tab shows how many items each customer is holding, as a
link opening the item list with a Release button. Release mirrors the
customer's own cart removal — drop the cart row, return the item to
available, guarded on 'reserved' so it can never resurrect a sold item —
and deliberately sends no email about an action the customer did not
take. The count is a subquery rather than another join, which would have
multiplied rows and inflated order_count and total_spent_cents.

The Inventory tab filters by category, tags, price, and status, reusing
the storefront's parser and query builder so the two cannot drift.
Reserved is one option in a Status filter rather than a standalone toggle.

Also fixes two defects the screenshots exposed: the reserved-count link
bubbled to the row handler and opened the customer drawer behind the
dialog, and .admin-category-node had no CSS at all, so the tree node name,
item count, and actions ran together as one string.

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

backend/src/itemFilters.ts

@@ -9,8 +9,16 @@ export interface ItemFilters {
   tagIds: number[];
   minPriceCents: number | null;
   maxPriceCents: number | null;
+  status: ItemStatus | null;
 }
 
+export type ItemStatus = 'available' | 'reserved' | 'sold';
+
+// Matched exactly, not case-insensitively: `items.status` only ever holds these
+// lowercase values, so accepting 'Reserved' would quietly return nothing rather
+// than reporting that the filter was wrong.
+const ITEM_STATUSES: readonly string[] = ['available', 'reserved', 'sold'];
+
 export interface BuiltFilter {
   clauses: string[];
   params: unknown[];
@@ -90,7 +98,16 @@ export function parseItemFilters(query: Record<string, unknown>): ItemFilters {
     throw new FilterError('min_price may not exceed max_price');
   }
 
-  return { categoryId, tagIds, minPriceCents, maxPriceCents };
+  const statusRaw = singleValue(query.status, 'status');
+  let status: ItemStatus | null = null;
+  if (statusRaw !== null && statusRaw !== '') {
+    if (!ITEM_STATUSES.includes(statusRaw)) {
+      throw new FilterError('invalid status');
+    }
+    status = statusRaw as ItemStatus;
+  }
+
+  return { categoryId, tagIds, minPriceCents, maxPriceCents, status };
 }
 
 // Returns WHERE fragments plus their parameters, with placeholders numbered
@@ -141,5 +158,11 @@ export function buildItemFilterSql(filters: ItemFilters, startIndex: number): Bu
     next++;
   }
 
+  if (filters.status !== null) {
+    params.push(filters.status);
+    clauses.push(`i.status = $${next}`);
+    next++;
+  }
+
   return { clauses, params };
 }