fix: brainstorm infinite loop, ghost cursor, embedding ::vector cast, semantic search, billing stats, usage meter accordion

- Fix useBrainstormSocket: stable guestId via useRef, remove setState in cleanup
- Fix GhostCursor: direct DOM manipulation via refs, no useState re-renders
- Fix all SQL embedding queries: add ::vector cast on text columns
- Fix embedding truncation to 15000 chars (under 8192 token limit)
- Fix NoteEmbedding INSERT: remove non-existent updatedAt column
- Fix billing page: show all quota stats in grid instead of single metric
- Fix usage meter: accordion expand/collapse, per-feature detail
- Fix semantic search: rebuild 103 note embeddings, ::vector cast on vectorSearch
- Fix brainstorm expand/manual-idea/create: ::vector cast on embedding SQL

memento-note/components/agents/agent-card.tsx

@@ -205,7 +205,7 @@ export function AgentCard({ agent, onEdit, onRefresh, onToggle }: AgentCardProps
     >
       <div className="flex items-start justify-between">
         <div className="flex items-center gap-4">
-          <div className="p-3 bg-muted rounded-xl group-hover:bg-foreground group-hover:text-background transition-all">
+          <div className="p-3 bg-muted rounded-xl group-hover:bg-brand-accent group-hover:text-white transition-all">
             <Icon className="w-5 h-5" />
           </div>
           <div className="space-y-1">
@@ -224,7 +224,7 @@ export function AgentCard({ agent, onEdit, onRefresh, onToggle }: AgentCardProps
           >
             <div className="relative inline-flex items-center cursor-pointer">
               <div className={`w-8 h-4 rounded-full transition-colors ${
-                agent.isEnabled ? 'bg-primary' : 'bg-muted-foreground/30'
+                agent.isEnabled ? 'bg-brand-accent' : 'bg-muted-foreground/30'
               }`}>
                 <span className={`absolute top-0.5 left-[2px] bg-background border border-muted-foreground/30 rounded-full h-3 w-3 transition-all ${
                   agent.isEnabled ? 'translate-x-4' : ''
@@ -260,9 +260,9 @@ export function AgentCard({ agent, onEdit, onRefresh, onToggle }: AgentCardProps
             <span className="uppercase tracking-tight">{t('agents.status.lastStatus')}</span>
             {lastAction ? (
               <span className={`flex items-center gap-1 ${
-                lastAction.status === 'success' ? 'text-primary'
+                lastAction.status === 'success' ? 'text-brand-accent'
                   : lastAction.status === 'failure' ? 'text-destructive'
-                    : lastAction.status === 'running' ? 'text-primary'
+                    : lastAction.status === 'running' ? 'text-brand-accent'
                       : 'text-muted-foreground'
               }`}>
                 {lastAction.status === 'success' && <Activity className="w-2 h-2" />}