gateway: bill Tinfoil's per-request charges on the audio paths

Tinfoil bills voxtral-tts $0.002 and whisper-large-v3-turbo $0.01 per REQUEST,
with $0 per token for both. Reading only the two token prices in its model list
made TTS look free and left STT billed at an older catalog's $0.05/1M tokens, so
neither matched what the co-op actually pays.

LiteLLM cannot express a per-request charge on the audio paths: per-request
pricing exists only on the search/rerank/MCP paths via input_cost_per_query, and
input_cost_per_request is read only by the proxy's cost-tracking settings, never
by the model cost calculator.

So patch_audio_request_cost.py, a build-time patch in the same shape as
patch_image_cost.py, makes response_cost_calculator honour a declared
input_cost_per_request. That function is the single funnel for every call type —
the proxy dispatches audio as `aspeech` and `transcription` and reaches it
through Logging._response_cost_calculator — so one insertion covers both. The
charge resolves from the per-deployment custom_pricing the logging layer builds
from our model_info, then the shared cost map, then call metadata, and the patch
is inert for any model that declares nothing.

config.yaml declares the real charges: $0.002/request for voxtral-tts, and
$0.01/request for whisper with its token price corrected to $0.

Verified before committing: the patch applies to the installed 1.103.2 anchors
and compiles; the helper's resolution order passes unit checks (all branches,
plus inert and garbage cases); the resulting config validates as YAML with all
12 entries intact. End-to-end spend is proven after deploy by a real TTS/STT call.

Refs code/litellm#5

config.yaml

@@ -148,7 +148,14 @@ 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: $0/1M tokens + $0.01 per request.
+  # voxtral-tts: $0/1M tokens + $0.002 per request.
+  # Tinfoil bills these per REQUEST (its model list carries a `requestPrice`);
+  # reading only the two token prices made TTS look free and left STT billed off
+  # an older catalog. LiteLLM cannot price per request on the audio paths, so
+  # patch_audio_request_cost.py (built in via the Dockerfile) makes the cost
+  # calculator honour `input_cost_per_request` below. Re-check that build log
+  # line after every LiteLLM upgrade.
   # 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.
@@ -159,7 +166,10 @@ model_list:
       api_key: os.environ/TINFOIL_API_KEY
     model_info:
       mode: audio_transcription
-      input_cost_per_token: 0.00000005
+      # Tinfoil: $0 per token, $0.01 per request. The per-request charge is the
+      # whole cost, and the patch is what makes it billable.
+      input_cost_per_token: 0
+      input_cost_per_request: 0.01
 
   - model_name: tinfoil/voxtral-tts
     litellm_params:
@@ -168,6 +178,8 @@ model_list:
       api_key: os.environ/TINFOIL_API_KEY
     model_info:
       mode: audio_speech
+      # Tinfoil: $0 per token, $0.002 per request — see the audio section note.
+      input_cost_per_request: 0.002
 
   # --- Embedding model (Tinfoil, in-TEE) ---
   # nomic-embed-text — 768-dim text embeddings for RAG/semantic search.