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/tests/unit/itemFilters.test.ts

@@ -6,7 +6,8 @@ describe('parseItemFilters', () => {
       categoryId: null,
       tagIds: [],
       minPriceCents: null,
-      maxPriceCents: null
+      maxPriceCents: null,
+      status: null
     });
   });
 
@@ -72,6 +73,25 @@ describe('parseItemFilters', () => {
   it('rejects a repeated query param rather than guessing which one to use', () => {
     expect(() => parseItemFilters({ category: ['1', '2'] })).toThrow(FilterError);
   });
+
+  it('parses each of the item statuses', () => {
+    expect(parseItemFilters({ status: 'available' }).status).toBe('available');
+    expect(parseItemFilters({ status: 'reserved' }).status).toBe('reserved');
+    expect(parseItemFilters({ status: 'sold' }).status).toBe('sold');
+  });
+
+  it('treats an absent or empty status as no status filter', () => {
+    expect(parseItemFilters({}).status).toBeNull();
+    expect(parseItemFilters({ status: '' }).status).toBeNull();
+  });
+
+  it('rejects a status outside the known set', () => {
+    expect(() => parseItemFilters({ status: 'pending' })).toThrow(FilterError);
+  });
+
+  it('rejects a status differing only by case, rather than silently coercing it', () => {
+    expect(() => parseItemFilters({ status: 'Reserved' })).toThrow(FilterError);
+  });
 });
 
 describe('buildItemFilterSql', () => {
@@ -100,6 +120,12 @@ describe('buildItemFilterSql', () => {
     expect(built.clauses.join(' ')).toContain('$3');
   });
 
+  it('filters on status', () => {
+    const built = buildItemFilterSql(parseItemFilters({ status: 'reserved' }), 1);
+    expect(built.clauses.join(' ')).toContain('i.status');
+    expect(built.params).toEqual(['reserved']);
+  });
+
   it('continues numbering across multiple filters', () => {
     const built = buildItemFilterSql(
       parseItemFilters({ category: '4', min_price: '100', max_price: '900' }),