Add ESLint + Prettier + EditorConfig tooling at repo root

v1.0 Phase 1.1 — repo-wide lint/format baseline.

- eslint.config.mjs (flat config) lints server, client, shared
- .prettierrc.json, .prettierignore, .editorconfig, .nvmrc
- Root package.json holds shared devDeps; per-package scripts keep
  their typecheck + test runners
- Fix 7 lint issues surfaced by the baseline run:
  - TicketDetail.tsx: replace ternary-with-side-effects with if/else
  - admin/Users.tsx: escape apostrophe in JSX
  - errorHandler.ts: typed err as unknown with ErrorLike refinement
  - users.ts: Prisma.UserUpdateInput instead of Record<string, any>
  - seed.ts: drop unused goddard binding
- Run prettier across tracked sources for a clean formatting baseline

client/src/components/AdminRoute.tsx

@@ -1,7 +1,7 @@
-import { Navigate, Outlet } from 'react-router-dom'
-import { useAuth } from '../contexts/AuthContext'
+import { Navigate, Outlet } from 'react-router-dom';
+import { useAuth } from '../contexts/AuthContext';
 
 export default function AdminRoute() {
-  const { user } = useAuth()
-  return user?.role === 'ADMIN' ? <Outlet /> : <Navigate to="/" replace />
+  const { user } = useAuth();
+  return user?.role === 'ADMIN' ? <Outlet /> : <Navigate to="/" replace />;
 }