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/(main)/template.tsx

@@ -0,0 +1,16 @@
+'use client'
+
+import { motion } from 'motion/react'
+
+export default function MainTemplate({ children }: { children: React.ReactNode }) {
+  return (
+    <motion.div
+      initial={{ opacity: 0, x: 20 }}
+      animate={{ opacity: 1, x: 0 }}
+      transition={{ duration: 0.3 }}
+      className="flex-1 flex flex-col min-h-0"
+    >
+      {children}
+    </motion.div>
+  )
+}