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/lab/lab-header.tsx

@@ -100,10 +100,10 @@ export function LabHeader({ canvases, currentCanvasId, onCreateCanvas }: LabHead
               <ChevronDown className="h-4 w-4 text-muted-foreground ms-2" />
             </Button>
           </DropdownMenuTrigger>
-          <DropdownMenuContent align="start" className="w-[280px] p-2 rounded-2xl shadow-xl border-muted/20">
+          <DropdownMenuContent align="start" className="w-[280px] p-2 rounded-2xl shadow-xl border-border/40 bg-paper dark:bg-dark-paper">
             <DropdownMenuLabel className="text-xs text-muted-foreground px-2 py-1.5 flex justify-between items-center">
               {t('labHeader.yourSpaces')}
-              <span className="text-[10px] bg-muted px-1.5 py-0.5 rounded-full font-mono">{canvases.length}</span>
+              <span className="text-[10px] bg-brand-accent/10 text-brand-accent px-1.5 py-0.5 rounded-full font-mono">{canvases.length}</span>
             </DropdownMenuLabel>
             <div className="space-y-1 mt-1">
               {canvases.map(c => (
@@ -111,13 +111,13 @@ export function LabHeader({ canvases, currentCanvasId, onCreateCanvas }: LabHead
                   <DropdownMenuItem 
                     className={cn(
                       "flex-1 flex flex-col items-start gap-0.5 rounded-xl cursor-pointer p-3 transition-all",
-                      c.id === currentCanvasId ? "bg-primary/5 text-primary border border-primary/20" : "hover:bg-muted"
+                      c.id === currentCanvasId ? "bg-brand-accent/5 text-brand-accent border border-brand-accent/20" : "hover:bg-muted/50"
                     )}
                     onClick={() => router.push(`/lab?id=${c.id}`)}
                   >
                     <div className="flex items-center gap-2 w-full justify-between">
                       <span className="font-semibold text-sm">{c.name}</span>
-                      {c.id === currentCanvasId && <span className="w-2 h-2 rounded-full bg-primary" />}
+                      {c.id === currentCanvasId && <span className="w-2 h-2 rounded-full bg-brand-accent" />}
                     </div>
                     <span className="text-[10px] text-muted-foreground">{t('labHeader.updated')} {new Date(c.updatedAt).toLocaleDateString()}</span>
                   </DropdownMenuItem>
@@ -139,7 +139,7 @@ export function LabHeader({ canvases, currentCanvasId, onCreateCanvas }: LabHead
             <DropdownMenuItem 
               onClick={handleCreate}
               disabled={isPending}
-              className="flex items-center gap-2 text-primary font-medium p-3 rounded-xl cursor-pointer hover:bg-primary/5"
+              className="flex items-center gap-2 text-brand-accent font-medium p-3 rounded-xl cursor-pointer hover:bg-brand-accent/5"
             >
               <Plus className="h-4 w-4" />
               {t('labHeader.newSpace')}