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/lib/queries/mutations.ts

@@ -92,7 +92,7 @@ async function performMutation<TIn, TOut>(opts: {
   return result.data as TOut;
 }
 
-export interface ApiMutationOptions<TIn, TOut> {
+export interface ApiMutationOptions<TIn> {
   url: string | ((input: TIn) => string);
   method: HttpMethod | ((input: TIn) => HttpMethod);
   /** Query-key prefixes to invalidate on success. Broad per CLAUDE.md. */
@@ -122,7 +122,7 @@ export interface ApiMutationOptions<TIn, TOut> {
  * as `ApiError` (with `.status` attached) so callers can branch on HTTP code.
  */
 export function useApiMutation<TIn, TOut>(
-  opts: ApiMutationOptions<TIn, TOut> &
+  opts: ApiMutationOptions<TIn> &
     Omit<UseMutationOptions<TOut, ApiError, TIn>, "mutationFn">,
 ) {
   const { url, method, invalidate, envelope, onSuccess, ...rest } = opts;

src/admin/lib/queries/plan.ts

@@ -1,5 +1,4 @@
 import { queryOptions } from "@tanstack/react-query";
-import apiFetch from "../../utils/api";
 import { jsonQuery } from "../apiAdapter";
 
 export interface PlanUser {