feat(server/openai/v1): structured request/delivered logging with requestId

The `/v1/openai/{chat,audio}` handlers used to be silent past
`hono/logger`'s `<-- POST` / `--> 502` lines — no userId, no model,
no token counts, no flux billed. Operators looking at a real gateway
incident had to cross-reference traces, request-log rows, and billing
ledger entries by timestamp alone. For a gateway whose value is
auditable per-request metering, that's not enough.

Hoists `requestId = nanoid()` to handler entry so the same
correlation id flows through:
- the inbound log line (model / stream / messageCount or inputChars
  for TTS)
- the per-stream / non-streaming delivered log (status / durationMs /
  promptTokens / completionTokens / fluxConsumed)
- the upstream-error degraded path (warn level)
- the partial-debit and debit-failure paths (already used requestId)
- `billingService.consumeFluxForLLM` / `ttsMeter.accumulate` for
  DB-level idempotency (replaces the previous local nanoid() calls)

handleListVoices gets a `debug`-level line — the route is high-
frequency from UI voice pickers and we don't want it in the regular
audit feed, but it's useful when chasing voice-picker drift bugs.

No new schemas, no metric emission changes; this is purely logger
output. Pairs with the cause-propagation change so errors carry the
upstream snippet AND the request can be traced end-to-end by id.

apps/server/src/routes/openai/v1/index.ts

@@ -119,6 +119,12 @@ export function createV1CompletionsRoutes(
   // the gate, concurrent requests are rejected before the upstream call.
   async function handleCompletion(c: Context<HonoEnv>) {
     const user = c.get('user')!
+    // Generated up-front so incoming, completion, partial-debit, debit-failure,
+    // and request-log entries all carry the same correlation id. Re-used as
+    // the billing requestId (both streaming and non-streaming branches) for
+    // DB-level idempotency.
+    const requestId = nanoid()
+
     // Read billing rates before pre-flight so the gate can compare against
     // the realistic per-request cost (fallback rate), not just `> 0`.
     const fallbackRate = await configKV.getOrThrow('FLUX_PER_REQUEST')
@@ -136,6 +142,15 @@ export function createV1CompletionsRoutes(
       requestModel = await configKV.getOrThrow('DEFAULT_CHAT_MODEL')
     }
 
+    const stream = !!body.stream
+    logger.withFields({
+      requestId,
+      userId: user.id,
+      model: requestModel,
+      stream,
+      messageCount: Array.isArray(body.messages) ? body.messages.length : undefined,
+    }).log('chat completion request')
+
     // Server-connection attrs come from the router (which knows the actual
     // upstream baseURL it dispatched to) — it enriches the active span with
     // its own `airi.gen_ai.gateway.*` attrs on success.
@@ -143,7 +158,7 @@ export function createV1CompletionsRoutes(
       attributes: {
         [GEN_AI_ATTR_OPERATION_NAME]: 'chat',
         [GEN_AI_ATTR_REQUEST_MODEL]: requestModel,
-        [AIRI_ATTR_GEN_AI_STREAM]: !!body.stream,
+        [AIRI_ATTR_GEN_AI_STREAM]: stream,
       },
     })
 
@@ -190,6 +205,10 @@ export function createV1CompletionsRoutes(
           stream: !!body.stream,
         },
       })
+
+      logger.withFields({ requestId, userId: user.id, model: requestModel, status: response.status, durationMs })
+        .warn('chat completion delivered with upstream error status')
+
       return new Response(response.body, {
         status: response.status,
         headers: buildSafeResponseHeaders(response),
@@ -200,7 +219,7 @@ export function createV1CompletionsRoutes(
     // `fallbackRate` / `fluxPer1kTokens` were hoisted to the top of this
     // function so the pre-flight gate can use them too.
 
-    if (body.stream) {
+    if (stream) {
       // Streaming: return response immediately, bill after stream ends
       const { readable, writable } = new TransformStream()
       const reader = response.body!.getReader()
@@ -302,7 +321,6 @@ export function createV1CompletionsRoutes(
             // race) or real DB errors. Partial debits are signalled via the
             // returned `charged < requested` and accounted to the same
             // `fluxUnbilled` counter (different `reason` label).
-            const requestId = nanoid()
             let actualCharged = 0
             try {
               const result = await billingService.consumeFluxForLLM({
@@ -367,6 +385,18 @@ export function createV1CompletionsRoutes(
                 stream_interrupted: streamInterrupted,
               },
             })
+
+            logger.withFields({
+              requestId,
+              userId: user.id,
+              model: requestModel,
+              status: response.status,
+              durationMs,
+              promptTokens: usage.promptTokens,
+              completionTokens: usage.completionTokens,
+              fluxConsumed: actualCharged,
+              stream: true,
+            }).log('chat completion delivered')
           }
         }
       })()
@@ -394,7 +424,6 @@ export function createV1CompletionsRoutes(
     // The upstream call has already happened (cost incurred), so partial
     // debit + `fluxUnbilled` is the only sane recovery — same shape as the
     // streaming path. `balance <= 0` still throws and bubbles up as 402.
-    const requestId = nanoid()
     const result = await billingService.consumeFluxForLLM({
       userId: user.id,
       amount: fluxConsumed,
@@ -443,11 +472,24 @@ export function createV1CompletionsRoutes(
       },
     })
 
+    logger.withFields({
+      requestId,
+      userId: user.id,
+      model: requestModel,
+      status: response.status,
+      durationMs,
+      promptTokens: usage.promptTokens,
+      completionTokens: usage.completionTokens,
+      fluxConsumed: result.charged,
+      stream: false,
+    }).log('chat completion delivered')
+
     return c.json(responseBody)
   }
 
   async function handleTTS(c: Context<HonoEnv>) {
     const user = c.get('user')!
+    const requestId = nanoid()
     const flux = await fluxService.getFlux(user.id)
     if (flux.flux <= 0) {
       throw createPaymentRequiredError('Insufficient flux')
@@ -463,6 +505,14 @@ export function createV1CompletionsRoutes(
       requestModel = await configKV.getOrThrow('DEFAULT_TTS_MODEL')
     }
 
+    logger.withFields({
+      requestId,
+      userId: user.id,
+      model: requestModel,
+      inputChars: inputText.length,
+      voice: typeof body.voice === 'string' ? body.voice : undefined,
+    }).log('tts speech request')
+
     // Pre-flight: refuse before hitting upstream if this segment would push the
     // user past their balance. Cheap-path requests below the Flux threshold
     // still pass when the user has at least 1 Flux.
@@ -506,6 +556,8 @@ export function createV1CompletionsRoutes(
       span.setStatus({ code: SpanStatusCode.ERROR, message: `Gateway ${response.status}` })
       span.end()
       recordMetrics({ model: requestModel, status: response.status, type: 'tts', durationMs, fluxConsumed: 0 })
+      logger.withFields({ requestId, userId: user.id, model: requestModel, status: response.status, durationMs })
+        .warn('tts speech delivered with upstream error status')
       return new Response(response.body, {
         status: response.status,
         headers: buildSafeResponseHeaders(response),
@@ -527,7 +579,7 @@ export function createV1CompletionsRoutes(
         userId: user.id,
         units: inputText.length,
         currentBalance: flux.flux,
-        requestId: nanoid(),
+        requestId,
         metadata: { model: requestModel },
       })
       fluxConsumed = result.fluxDebited
@@ -546,6 +598,16 @@ export function createV1CompletionsRoutes(
       fluxConsumed,
     })
 
+    logger.withFields({
+      requestId,
+      userId: user.id,
+      model: requestModel,
+      status: response.status,
+      durationMs,
+      inputChars: inputText.length,
+      fluxConsumed,
+    }).log('tts speech delivered')
+
     return new Response(response.body, {
       status: response.status,
       headers: buildSafeResponseHeaders(response),
@@ -566,6 +628,10 @@ export function createV1CompletionsRoutes(
 
     const voices = await llmRouter.listTtsVoices(model)
     const recommended = (await configKV.getOptional('DEFAULT_TTS_VOICES')) ?? {}
+    // Debug level: high-frequency catalog poll from UI selectors, no
+    // billing / user-facing side effect — useful only when debugging
+    // voice-picker drift, never as a permanent audit trail line.
+    logger.withFields({ model, voiceCount: voices.length }).debug('list tts voices')
     return Response.json({ voices, recommended })
   }