chore(lint): remove all 34 dead-code warnings (verified site by site)

unused-vars (25): leftover imports/types across pages, routes and services;
write-only sickHours accumulator; unused holidayCount pair; test helpers
authPatch/authDelete; TOut dropped from ApiMutationOptions (the hook keeps
its own generic — no call-site changes); requireAuth no longer importable
in customers/warehouse routes (matches the no-bare-auth-reads convention).

useless-assignment (5): initializers proven overwritten on every path
(systemQty x2, hours, writtenSize -> let x: number) and the seed's dead
adminUser reassignment (create kept, assignment dropped).

useless-escape (4): [eE+\-] -> [eE+-] and [\/...] -> [/...] — identical
semantics.

Behavior-neutral; lint 102 -> 68 warnings (0 errors), suite 641 green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/routes/admin/customers.ts

@@ -1,6 +1,6 @@
 import { FastifyInstance } from "fastify";
 import prisma from "../../config/database";
-import { requireAuth, requirePermission } from "../../middleware/auth";
+import { requirePermission } from "../../middleware/auth";
 import { logAudit } from "../../services/audit";
 import { success, error, parseId, paginated } from "../../utils/response";
 import { parsePagination, buildPaginationMeta } from "../../utils/pagination";