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/app/api/usage/current/route.ts

@@ -1,6 +1,6 @@
 import { NextResponse } from 'next/server';
 import { auth } from '@/auth';
-import { getUserQuotas } from '@/lib/entitlements';
+import { getUserQuotas, getEffectiveTier } from '@/lib/entitlements';
 
 export async function GET() {
   const session = await auth();
@@ -10,8 +10,11 @@ export async function GET() {
   }
 
   try {
-    const quotas = await getUserQuotas(session.user.id);
-    return NextResponse.json({ quotas });
+    const [quotas, tier] = await Promise.all([
+      getUserQuotas(session.user.id),
+      getEffectiveTier(session.user.id),
+    ]);
+    return NextResponse.json({ quotas, tier });
   } catch (error) {
     console.error('[usage/current] Failed to fetch quotas:', error);
     return NextResponse.json(