refactor: standardise antd imports and remove the avoidable any (#65)

Stage 1 of #65: this issue's original two lists. The type-checked gate it also owns follows in later stages.

Nine files imported antd from the barrel while the rest of the codebase used deep imports from antd/es. Both resolve to the same modules under antd v5 and Vite, so this is not the tree-shaking problem it would have been under v4 — the cost was that a documented convention had two spellings, and nobody reading a file could tell whether its style was deliberate or just old. Eighty-two imports converted, and every antd/es path was checked to exist before generating any of them rather than trusting a name-mangling rule.

The three `client: any` parameters in cartCheckout are now PoolClient. These functions run inside a transaction, and `any` removed exactly the check that would catch a pool-versus-client mix-up — which in this codebase means a query silently running outside the transaction it was meant to be part of, on the path that takes money.

publicCustomer took `any` and now takes a CustomerRow describing what it actually reads. Typed as its own shape rather than the whole table so that adding a column later — a password hash, a token, an internal note — cannot quietly start being echoed back to a customer.

The three `(window as any).paypal` casts are replaced by a declared interface for the injected SDK. It is deliberately narrow: it describes the three things this app calls, not the whole SDK, because a wider guess would be fiction and a wrong shape typed confidently is worse than an honest cast. The property is optional, since the SDK is absent until its script has loaded — which is the check both call sites already make.

Verified: 141 unit, 169 integration and 94 end-to-end passing. The end-to-end run is the one that matters here — an antd import migration can build cleanly and still break at runtime through styles or context, so a green tsc proves less than it appears to.

Lint drops from 8 warnings to 4 in the backend and 30 to 27 in the frontend, all of them the no-explicit-any this change removed. As a side effect the no-unsafe count that later stages exist to clear falls from 259 to 216 in the backend and 73 to 67 in the frontend, measured rather than estimated.

Refs #65
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/components/ItemCard.tsx

@@ -1,5 +1,13 @@
 import { useState, useRef } from 'react';
-import { Card, Badge, Typography, Carousel, Button, message, Tag, Modal, Tooltip } from 'antd';
+import Card from 'antd/es/card';
+import Badge from 'antd/es/badge';
+import Typography from 'antd/es/typography';
+import Carousel from 'antd/es/carousel';
+import Button from 'antd/es/button';
+import message from 'antd/es/message';
+import Tag from 'antd/es/tag';
+import Modal from 'antd/es/modal';
+import Tooltip from 'antd/es/tooltip';
 import { LeftOutlined, RightOutlined, HeartOutlined, HeartFilled } from '@ant-design/icons';
 import type { CarouselRef } from 'antd/es/carousel';
 import { Item } from '../api';