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/embedding.service.ts

@@ -15,16 +15,24 @@ export interface EmbeddingResult {
 
 export class EmbeddingService {
   private readonly EMBEDDING_DIMENSION = 1536
+  private readonly MAX_CHARS = 15000
+
+  private truncateForEmbedding(text: string): string {
+    if (text.length <= this.MAX_CHARS) return text
+    return text.slice(0, this.MAX_CHARS)
+  }
 
   async generateEmbedding(text: string): Promise<EmbeddingResult> {
     if (!text || text.trim().length === 0) {
       throw new Error('Cannot generate embedding for empty text')
     }
 
+    const truncated = this.truncateForEmbedding(text)
+
     try {
       const config = await getSystemConfig()
       const embedding = await withAiProviderFallback('embedding', config, (provider) =>
-        provider.getEmbeddings(text)
+        provider.getEmbeddings(truncated)
       )
 
       return {
@@ -41,7 +49,7 @@ export class EmbeddingService {
   async generateBatchEmbeddings(texts: string[]): Promise<EmbeddingResult[]> {
     if (!texts || texts.length === 0) return []
 
-    const validTexts = texts.filter(t => t && t.trim().length > 0)
+    const validTexts = texts.filter(t => t && t.trim().length > 0).map(t => this.truncateForEmbedding(t))
     if (validTexts.length === 0) return []
 
     try {