fix(quotas): unifier le décompte IA (BYOK, rollback) et combler les fuites

Centralise la réserve via ai-quota, corrige admin unavailable (-1), brancher les routes sans quota et le host-pays brainstorm, avec usage-meter élargi, noms de clusters, MCP et ajustements dashboard/insights.

Co-authored-by: Cursor <cursoragent@cursor.com>

memento-note/lib/ai-quota.ts

@@ -0,0 +1,135 @@
+import { willUseByokForLane } from '@/lib/ai/provider-for-user'
+import type { AiFeatureLane } from '@/lib/ai/router'
+import { getSystemConfig } from '@/lib/config'
+import {
+  reserveUsageOrThrow,
+  releaseUsage,
+  checkSessionEntitlementOrThrow,
+  QuotaExceededError,
+  QuotaServiceUnavailableError,
+} from '@/lib/entitlements'
+import type { FeatureName } from '@/lib/quota-utils'
+import { emitAiUsageChanged } from '@/lib/ai-usage-sync'
+
+export type ReserveAiUsageOptions = {
+  lane?: AiFeatureLane
+  /** Defaults to userId — host-pays brainstorm bills this account. */
+  billingUserId?: string
+}
+
+/** Reserve one AI unit; skips when BYOK will be used for the lane. */
+export async function reserveAiUsageOrThrow(
+  userId: string,
+  feature: FeatureName,
+  options?: ReserveAiUsageOptions,
+): Promise<{ usedByok: boolean; billedUserId: string }> {
+  const billedUserId = options?.billingUserId ?? userId
+  const lane = options?.lane ?? 'chat'
+  const config = await getSystemConfig()
+  const { usedByok } = await willUseByokForLane(lane, config, billedUserId)
+  if (!usedByok) {
+    await reserveUsageOrThrow(billedUserId, feature)
+  }
+  return { usedByok, billedUserId }
+}
+
+/** Host-pays: reserve on session owner with guest metadata on 402. */
+export async function reserveSessionAiUsageOrThrow(
+  billingOwnerId: string,
+  triggeredByUserId: string,
+  isGuestActor: boolean,
+  feature: FeatureName,
+  options?: { lane?: AiFeatureLane },
+): Promise<{ usedByok: boolean }> {
+  const lane = options?.lane ?? 'chat'
+  const config = await getSystemConfig()
+  const { usedByok } = await willUseByokForLane(lane, config, billingOwnerId)
+  if (!usedByok) {
+    await checkSessionEntitlementOrThrow(
+      billingOwnerId,
+      triggeredByUserId,
+      isGuestActor,
+      feature,
+    )
+  }
+  return { usedByok }
+}
+
+/** Run fn under quota; releases the unit if fn throws (unless BYOK). */
+export async function withAiQuota<T>(
+  userId: string,
+  feature: FeatureName,
+  fn: () => Promise<T>,
+  options?: ReserveAiUsageOptions,
+): Promise<T> {
+  const { usedByok, billedUserId } = await reserveAiUsageOrThrow(userId, feature, options)
+  try {
+    const result = await fn()
+    if (!usedByok) {
+      emitAiUsageChanged()
+    }
+    return result
+  } catch (err) {
+    if (!usedByok) {
+      await releaseUsage(billedUserId, feature)
+    }
+    throw err
+  }
+}
+
+/** Host-pays collaborative flows (brainstorm) with rollback on failure. */
+export async function withSessionAiQuota<T>(
+  billingOwnerId: string,
+  triggeredByUserId: string,
+  isGuestActor: boolean,
+  feature: FeatureName,
+  fn: () => Promise<T>,
+  options?: { lane?: AiFeatureLane },
+): Promise<T> {
+  const { usedByok } = await reserveSessionAiUsageOrThrow(
+    billingOwnerId,
+    triggeredByUserId,
+    isGuestActor,
+    feature,
+    options,
+  )
+  try {
+    const result = await fn()
+    if (!usedByok) {
+      emitAiUsageChanged()
+    }
+    return result
+  } catch (err) {
+    if (!usedByok) {
+      await releaseUsage(billingOwnerId, feature)
+    }
+    throw err
+  }
+}
+
+export function isQuotaError(err: unknown): err is QuotaExceededError {
+  return err instanceof QuotaExceededError
+}
+
+export function quotaExceededJson(err: QuotaExceededError) {
+  return err.toJSON()
+}
+
+export function quotaErrorStatus() {
+  return 402
+}
+
+/** Standard Next.js / Response handlers for quota errors. */
+export function handleQuotaHttpError(err: unknown): Response | null {
+  if (err instanceof QuotaExceededError) {
+    return Response.json(err.toJSON(), { status: 402 })
+  }
+  if (err instanceof QuotaServiceUnavailableError) {
+    return Response.json({ error: err.code }, { status: 503 })
+  }
+  return null
+}
+
+export function notifyAiUsageChanged(): void {
+  emitAiUsageChanged()
+}