feat: Studio bulk ops, perf fixes, bug fixes, confirm dialog visibility

Confirm Dialog:
- Overlay opacity 80% -> 95% (solid black)
- Card uses bg-surface with glow shadow ring-primary/40
- Added AlertTriangle icon for danger variant
- Removed backdrop-blur for maximum opacity

Studio features:
- Bulk delete: select imported items and delete in batch
- Bulk nitro regen: select items missing .nitro and regenerate all
- Added Trash2 and RefreshCw toolbar buttons for bulk actions

Performance:
- BatchProgress: React.memo + useMemo for entries/total/completed/percent
- BatchProgress: ETA interval uses useRef to avoid re-creation per completed
- CatalogRail: React.memo + useCallback for toggle
- Removed redundant double setBatchProgress calls
- Removed redundant new Map(initial) wrapping

Bug fixes:
- importBatch: stale batchDone closure always cleared progress panel (use ref)
- importBatch: added missing toast.error on HTTP failure
- bulkRegenNitro: now checks per-item results instead of marking all as succeeded
- single deleteItem: now removes classname from selected set
- retryFailed: clears progress panel on HTTP error and stream error
- Removed unused 'done' variable (2x) from cloneAllMissing/retryFailed

Lint:
- biome format fixes for selectedMissingNitro and setItems

src/components/admin/confirm-dialog.tsx

@@ -1,5 +1,6 @@
 "use client";
 
+import { AlertTriangle } from "lucide-react";
 import { AnimatePresence, motion } from "motion/react";
 import { useCallback, useEffect, useRef, useState } from "react";
 import { createPortal } from "react-dom";
@@ -77,7 +78,7 @@ export function ConfirmDialog({
 					<button
 						type="button"
 						aria-label="Dismiss"
-						className="absolute inset-0 bg-black/80 backdrop-blur-sm"
+						className="absolute inset-0 bg-black/95"
 						disabled={isLoading}
 						onClick={() => {
 							if (!isLoading) onOpenChange(false);
@@ -89,19 +90,26 @@ export function ConfirmDialog({
 						aria-modal="true"
 						aria-labelledby="confirm-dialog-title"
 						aria-describedby="confirm-dialog-desc"
-						className="relative z-10 w-full max-w-md rounded-lg border border-border bg-background/100 p-6 text-card-foreground shadow-2xl ring-1 ring-black/10 backdrop-blur-none"
+						className="relative z-10 w-full max-w-md rounded-xl border-2 border-primary/40 bg-surface p-6 text-card-foreground shadow-[0_0_60px_-10px_rgba(245,158,11,0.3)]"
 						variants={modalContentVariants}
 						initial="hidden"
 						animate="visible"
 						exit="exit"
 					>
 						<div className="flex flex-col gap-2 text-left">
-							<h2
-								id="confirm-dialog-title"
-								className="text-lg font-semibold leading-none"
-							>
-								{title}
-							</h2>
+							<div className="flex items-center gap-3">
+								{variant === "danger" && (
+									<div className="flex h-10 w-10 shrink-0 items-center justify-center rounded-full bg-destructive/15">
+										<AlertTriangle className="h-5 w-5 text-destructive" />
+									</div>
+								)}
+								<h2
+									id="confirm-dialog-title"
+									className="text-lg font-semibold leading-none"
+								>
+									{title}
+								</h2>
+							</div>
 							<p
 								id="confirm-dialog-desc"
 								className="text-sm text-muted-foreground"