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/project-files.ts

@@ -199,7 +199,7 @@ export default async function projectFilesRoutes(
 
       const subPath = parsedQuery.data.path || "";
       const rawFileName = file.filename;
-      const fileName = rawFileName.replace(/[\/\\:*?"<>|]/g, "_");
+      const fileName = rawFileName.replace(/[/\\:*?"<>|]/g, "_");
 
       const buffer = await file.toBuffer();
       const err = await fm.uploadFile(