[diegosouzapw]

Closes #12574

Root cause

The three ElevenLabs-backed /v1/* routes (speech-to-text, text-to-speech/[voiceId],
voices) all funnel through the shared proxyElevenLabsRequest() in
src/app/api/v1/_shared/elevenLabsProxy.ts, which went straight from credential lookup to
the upstream fetch() and never called enforceApiKeyPolicy(). Every other billable
/v1/* route (images, audio, videos, music, ocr, rerank, moderations, embeddings, search,
etc.) calls enforceApiKeyPolicy before dispatch. Because the clientApiPolicy middleware
only validates key validity/ban/expiry (not budget, custom rate limits, schedule windows, or
allowedEndpoints), any valid API key could call these three routes completely unconstrained
by an operator's budget caps or rate limits.

A second, related gap: even with enforceApiKeyPolicy() added, allowedEndpoints scoping
would still no-op on these three routes because ENDPOINT_CATEGORIES
(src/shared/constants/endpointCategories.ts) only mapped /v1/audio to the audio
category — resolveEndpointCategory() returned null for /v1/speech-to-text,
/v1/text-to-speech, and /v1/voices, so validateEndpointAccess() never fired for them.

Fix

• src/app/api/v1/_shared/elevenLabsProxy.ts: call enforceApiKeyPolicy(request, null) at
  the top of proxyElevenLabsRequest(), before the credential lookup, matching the pattern
  used by 21 sibling /v1/* routes (e.g. src/app/api/v1/images/upscale/route.ts). A
  rejected key never touches ElevenLabs credentials or issues an upstream request.
• src/shared/constants/endpointCategories.ts: added a new elevenlabs category with
  prefixes /v1/speech-to-text, /v1/text-to-speech, /v1/voices — a dedicated category
  rather than extending audio, so existing keys already scoped to audio (expecting only
  /v1/audio/*) are not silently widened.
• tests/unit/elevenlabs-policy.test.ts (new): budget-exceeded key gets 429 on all three
  routes without reaching upstream; a key scoped away from the elevenlabs category gets
  403 on all three routes; an unrestricted key still proxies through successfully.
• tests/unit/endpoint-categories.test.ts: added 3 cases asserting
  resolveEndpointCategory() now maps the three ElevenLabs paths to elevenlabs instead of
  null.

Regression test — RED → GREEN

node --import tsx/esm --test tests/unit/elevenlabs-policy.test.ts

RED (on unfixed code, verified by temporarily reverting the two production files):

✖ an over-budget key is rejected with 429 on all three ElevenLabs routes without reaching upstream
  AssertionError: 200 !== 429
✖ a key scoped away from the elevenlabs category is rejected with 403 on all three routes
  AssertionError: 200 !== 403

GREEN (with the fix):

✔ an over-budget key is rejected with 429 on all three ElevenLabs routes without reaching upstream
✔ a key scoped away from the elevenlabs category is rejected with 403 on all three routes
✔ an unrestricted key still proxies through to the upstream successfully
ℹ tests 3
ℹ pass 3
ℹ fail 0

Gates run (all green)

• node scripts/check/check-file-size.mjs — OK, no frozen file grown
• node scripts/check/check-complexity.mjs — OK (2799 violations vs baseline 3218)
• node scripts/check/check-cognitive-complexity.mjs — OK (1265 violations vs baseline 1437)
• npm run typecheck:core — exit 0
• npx eslint --suppressions-location config/quality/eslint-suppressions.json <changed files> — exit 0
• tests/unit/elevenlabs-policy.test.ts (new) — 3/3 pass
• tests/unit/endpoint-categories.test.ts (existing + 3 new cases) — 29/29 pass
• tests/unit/endpoint-restrictions-policy.test.ts (existing) — 11/11 pass
• tests/unit/api-key-policy.test.ts (existing) — 41/41 pass
• tests/unit/elevenlabs-native-routes.test.ts (existing) — 6/6 pass, no regression
• node scripts/check/check-changelog-integrity.mjs — OK

⚠️ base-red inherited: #12732 — unit #12058, integration codex-cache, package-artifact, tarball-smoke, agent-skills-sync