voxtral-tts: bill speech at the model's published rate ($16/1M characters)

Tinfoil's catalog lists voxtral-tts at $0/$0, so the entry declared no cost at
all and speech usage never consumed member allowance — voice mode was free
against the member budget while every other capability was metered. The OWUI
precedent was to bill TTS like anything else, so set the field.

input_cost_per_character: 0.000016 = $16/1M characters, from LiteLLM's bundled
map for the same weights (mistral/voxtral-mini-tts-*, sourced to Mistral's model
card) and the field OpenAI's TTS entries use on this adapter.

Revisit if the Tinfoil invoice shows a different number, and note the policy
question: Tinfoil may be serving this model beta-free, so members would be
consuming allowance for a resource the co-op is not paying for.

config.yaml

@@ -148,7 +148,13 @@ model_list:
   # models: the member portal's /v1/models filters them out of the chat model
   # list (see AUDIO_MODEL_PREFIXES there) so members don't see them in the
   # picker, but they remain fully callable via /v1/audio/* for API users.
-  # whisper-large-v3-turbo: $0.05/1M input tokens. voxtral-tts: listed $0/$0.
+  # whisper-large-v3-turbo: $0.05/1M input tokens. voxtral-tts: Tinfoil's
+  # catalog lists it $0/$0 and every cost field was left NULL, so speech usage
+  # never consumed member allowance. Billed at the model's published rate
+  # instead: $16/1M characters, i.e. LiteLLM's own bundled price for the same
+  # weights (mistral/voxtral-mini-tts-*, sourced to Mistral's model card) and
+  # the rate OpenAI's TTS entries use for the same field. Revisit if the
+  # Tinfoil invoice shows a different number.
   # NOTE: LiteLLM routes audio by the openai/ provider + the endpoint called
   # (/v1/audio/transcriptions or /v1/audio/speech) — there is no
   # "audio_transcription/" provider prefix.
@@ -168,6 +174,10 @@ model_list:
       api_key: os.environ/TINFOIL_API_KEY
     model_info:
       mode: audio_speech
+      # $16 per 1M characters. This is the field LiteLLM reads for speech on the
+      # openai adapter (same key OpenAI's tts-1 uses upstream), so member spend
+      # and budget caps now account for voice mode.
+      input_cost_per_character: 0.000016
 
   # --- Embedding model (Tinfoil, in-TEE) ---
   # nomic-embed-text — 768-dim text embeddings for RAG/semantic search.