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/admin/pages/AttendanceHistory.tsx

@@ -1,5 +1,5 @@
 import { useState, useMemo, useRef } from "react";
-import { useQuery, useQueryClient } from "@tanstack/react-query";
+import { useQuery } from "@tanstack/react-query";
 import Box from "@mui/material/Box";
 import Typography from "@mui/material/Typography";
 import { useAuth } from "../context/AuthContext";
@@ -9,7 +9,6 @@ import { iconBadgeSx } from "../theme";
 import {
   attendanceHistoryOptions,
   type AttendanceRecord,
-  type ProjectLogEntry,
 } from "../lib/queries/attendance";
 import {
   formatDate,
@@ -201,7 +200,6 @@ const renderProjectCell = (record: AttendanceRecord) => {
 
 export default function AttendanceHistory() {
   const { user, hasPermission } = useAuth();
-  const queryClient = useQueryClient();
   const { data: companySettings } = useQuery(companySettingsOptions());
   const companyName = companySettings?.company_name || "";
   const printRef = useRef<HTMLDivElement>(null);