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/lib/ai/services/memory-echo.service.ts

@@ -77,14 +77,14 @@ export class MemoryEchoService {
       for (const note of notesWithoutEmbeddings) {
         if (!note.content || note.content.trim().length === 0) continue
         try {
-          const embedding = await provider.getEmbeddings(note.content)
+          const embedding = await provider.getEmbeddings(note.content.slice(0, 15000))
           if (embedding && embedding.length > 0) {
             const vecStr = `[${embedding.join(',')}]`
             await prisma.$executeRawUnsafe(
-              `INSERT INTO "NoteEmbedding" ("id", "noteId", "embedding", "createdAt", "updatedAt")
-               VALUES (gen_random_uuid(), $1, $2::vector, now(), now())
+              `INSERT INTO "NoteEmbedding" ("id", "noteId", "embedding", "createdAt")
+               VALUES (gen_random_uuid(), $1, $2::vector, now())
                ON CONFLICT ("noteId")
-               DO UPDATE SET "embedding" = $2::vector, "updatedAt" = now()`,
+               DO UPDATE SET "embedding" = $2::vector`,
               note.id,
               vecStr
             )