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/plan-entitlements.ts

@@ -3,6 +3,9 @@ import { VALID_FEATURES } from './quota-utils';
 
 export type SubscriptionTier = 'BASIC' | 'PRO' | 'BUSINESS' | 'ENTERPRISE';
 
+/** Stored in PlanEntitlement.limitValue — feature explicitly disabled via admin. */
+export const ENTITLEMENT_UNAVAILABLE = -1;
+
 /** Hardcoded defaults — used when DB is empty or unavailable. */
 export const FALLBACK_TIER_LIMITS: Record<
   SubscriptionTier,
@@ -98,18 +101,24 @@ function buildLimitMapFromRows(
 
   for (const row of rows) {
     map[row.tier][row.feature] =
-      row.limitValue === null ? Infinity : row.limitValue;
+      row.limitValue === null
+        ? Infinity
+        : row.limitValue === ENTITLEMENT_UNAVAILABLE
+          ? ENTITLEMENT_UNAVAILABLE
+          : row.limitValue;
   }
 
   return map;
 }
 
-/** Merge DB entitlements with FALLBACK for features added after admin seeding. */
+/** Merge DB entitlements with FALLBACK for features added after admin seeding.
+ *  Does NOT override ENTITLEMENT_UNAVAILABLE (-1) or explicit limits. */
 function mergeWithFallback(map: LimitMap): LimitMap {
   const fallback = fallbackToLimitMap();
   for (const tier of Object.keys(fallback) as SubscriptionTier[]) {
     for (const [feature, limit] of Object.entries(fallback[tier])) {
-      if (map[tier][feature] === undefined) {
+      const current = map[tier][feature];
+      if (current === undefined) {
         map[tier][feature] = limit;
       }
     }
@@ -157,7 +166,7 @@ export async function getLimitAsync(
 ): Promise<number | undefined> {
   const map = await loadLimitMap();
   const limit = map[tier]?.[feature];
-  if (limit === undefined) return undefined;
+  if (limit === undefined || limit === ENTITLEMENT_UNAVAILABLE) return undefined;
   if (limit === Infinity) return Infinity;
   return limit;
 }
@@ -184,9 +193,11 @@ export async function getAllEntitlementsForAdmin(): Promise<
       feature: r.feature,
       limitValue: r.limitValue,
       mode:
-        r.limitValue === null
-          ? ('unlimited' as const)
-          : ('limited' as const),
+        r.limitValue === ENTITLEMENT_UNAVAILABLE
+          ? ('unavailable' as const)
+          : r.limitValue === null
+            ? ('unlimited' as const)
+            : ('limited' as const),
     }));
   }