chore(usage): remove unused fetchUsage()

CLAUDE.md

@@ -52,7 +52,7 @@
 - JSON-LD parent organization is Yivi (not Radboud University).
 - Outlook-tab copy on `/addons` lives in `src/lib/locales/{en,nl}.json` under `addons.Outlook` (one HTML string) — append new `<li>` items at the end of the `<ol>`.
 - The recipient notification email is generated in `encryption4all/cryptify` (`src/email.rs` + `templates/email/*`), NOT here — `EmailPreviewModal.svelte` only previews cryptify's rendered HTML. And a user complaint about a small/hard-to-copy "code" in an email is usually the Yivi email-attribute verification flow (privacybydesign/irmamobile epic #598), not cryptify's download link — check there before routing.
-- `UsageWarning` fires when the SENDER's email becomes known (after `pg.sign.yivi(...)` with `includeSender: true`) — never probe on the first recipient email; quotas are per-sender. Server 413 on `POST /fileupload/finalize/<uuid>` is the authoritative backstop.
+- There is no live pre-flight usage probe. Sender quotas (per-sender) are enforced by the server 413 on `POST /fileupload/finalize/<uuid>` — parsed by `parseLimitExceededBody` in `src/lib/usage.ts` — with a browser-local estimate in `src/lib/localUsage.ts` for the warning ahead of upload. A `GET /usage` client (`fetchUsage`) and a `UsageWarning` component were sketched but never wired into the UI; the `fetchUsage` remnant was removed (see #323).
 
 ## Before claiming tests green
 

src/lib/usage.ts

@@ -1,4 +1,4 @@
-import { FILEHOST_URL, ROLLING_LIMIT } from '$lib/env'
+import { ROLLING_LIMIT } from '$lib/env'
 
 /**
  * Response shape of `GET /usage?email=...` on the cryptify backend (see encryption4all/cryptify#100).
@@ -37,31 +37,6 @@ export function classifyUsage(u: UsageResponse): UsageStatus {
     }
 }
 
-/**
- * Fetch the current sender usage from cryptify. Returns null when the endpoint is
- * unreachable or unavailable (e.g. backend not yet deployed) so the UI degrades quietly.
- * `signal` lets callers cancel in-flight requests when the user keeps typing.
- */
-export async function fetchUsage(
-    email: string,
-    signal?: AbortSignal
-): Promise<UsageStatus | null> {
-    try {
-        const url = `${FILEHOST_URL}/usage?email=${encodeURIComponent(email)}`
-        const res = await fetch(url, { signal, credentials: 'omit' })
-        if (!res.ok) return null
-        const body = (await res.json()) as UsageResponse
-        if (
-            typeof body.used_bytes !== 'number' ||
-            typeof body.limit_bytes !== 'number'
-        )
-            return null
-        return classifyUsage(body)
-    } catch {
-        return null
-    }
-}
-
 /**
  * Parse a cryptify 413 "limit exceeded" response body into a UsageStatus when possible.
  * Falls back to a synthetic "blocked at `ROLLING_LIMIT`" status so the UI can still show