feat(billing): enforce image generation quota with admin API and user display

Add period_images_bonus and ledger tracking, gate image_make on remaining quota,
expose admin image-quota routes, show remaining image quota in the balance popover,
and document that admin UI must live in memind_adm (5174) not ops.

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

src/types.ts

@@ -304,6 +304,9 @@ export type ActiveSubscription = {
   status: 'active' | 'expired' | 'cancelled';
   periodTokensLimit: number;
   periodTokensUsed: number;
+  periodImagesLimit: number;
+  periodImagesUsed: number;
+  periodImagesBonus?: number;
   periodStart: number;
   periodEnd: number;
   expiresAt: number;
@@ -317,6 +320,7 @@ export type PlanDefinition = {
   priceCents: number;
   periodDays: number;
   periodTokens: number;
+  periodImages?: number;
   modelTier: string;
   overageRate: number;
 };