docs(env): remove runtime-only TTS and compute rate limit settings from env var docs

Eliminate documentation of TTS and compute PDF parsing rate limiting options from the environment variables reference, as these are managed exclusively via runtime configuration in the admin UI and do not correspond to environment variables. This clarifies the distinction between environment-based and runtime-managed settings.

docs-site/docs/reference/environment-variables.md

@@ -96,27 +96,6 @@ Optional first-boot bootstrap API key for the auto-created `default-openai` shar
 - Stored encrypted at rest after bootstrap.
 - After bootstrap, provider configuration is DB-backed and managed in **Settings → Admin → Shared providers**.
 
-### TTS Daily Rate Limiting (Runtime Settings)
-
-Managed as runtime config in **Settings → Admin → Site features**.
-
-- `disableTtsRateLimit` default: `true` (daily TTS limits disabled)
-- `ttsDailyLimitAnonymous` default: `50000`
-- `ttsDailyLimitAuthenticated` default: `500000`
-- `ttsIpDailyLimitAnonymous` default: `100000`
-- `ttsIpDailyLimitAuthenticated` default: `1000000`
-
-### TTS Upstream Settings (Runtime Settings)
-
-Managed as runtime config in **Settings → Admin → Site features → TTS upstream**.
-
-- `ttsUpstreamMaxRetries` default: `2`
-- `ttsUpstreamTimeoutMs` default: `285000`
-- `ttsCacheMaxSizeBytes` default: `268435456` (256 MB)
-- `ttsCacheTtlMs` default: `1800000` (30 minutes)
-
-There are no dedicated env vars for these runtime settings.
-
 ## Auth and Identity
 
 ### BASE_URL
@@ -339,19 +318,6 @@ External compute worker URL.
 
 Shared token for app-to-external-worker requests.
 
-## Compute PDF Parsing Rate Limiting (Runtime Settings)
-
-Managed as runtime config in **Settings → Admin → Site features**.
-
-- `disableComputeRateLimit` default: `true`
-- `computeParseBurstMax` default: `8`
-- `computeParseBurstWindowSec` default: `60`
-- `computeParseSustainedMax` default: `24`
-- `computeParseSustainedWindowSec` default: `600`
-- `maxUploadMb` default: `200`
-
-There are no dedicated env vars for these runtime settings.
-
 ## Audio Runtime
 
 ### FFMPEG_BIN