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

Dockerfile

@@ -35,6 +35,14 @@ RUN python3 /app/code/patch_budget_message.py
 COPY patch_image_cost.py /app/code/patch_image_cost.py
 RUN python3 /app/code/patch_image_cost.py
 
+# Audio per-request pricing: Tinfoil bills voxtral-tts and whisper per request,
+# which LiteLLM cannot express on the audio paths, so those two were billed at
+# $0. The patch makes the cost calculator honour a declared
+# input_cost_per_request. Check for the "[coop-patch] applied" line in the build
+# log after upgrading LiteLLM: the script is non-fatal and warns instead.
+COPY patch_audio_request_cost.py /app/code/patch_audio_request_cost.py
+RUN python3 /app/code/patch_audio_request_cost.py
+
 # Audio keep-alive: scheduled pings keep the Tinfoil TEE audio enclave
 # warm so voice mode skips the ~24s cold-start (see audio_keepalive.py header).
 COPY audio_keepalive.py /app/code/audio_keepalive.py