fix(dashboard): cut duplicate API/icon spam, lazy-load provider assets

Share one /api/models fetch via useModelCaps cache, mount ModelSelectModal
only when open, stop double fetchModelAliases on CLI tool cards, and resolve
provider icons through a session 404 cache with missing PNGs + loading=lazy.
Also include Claude Exa MCP toggle (claude-settings + ClaudeToolCard) that
was already in the working tree.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/app/(dashboard)/dashboard/basic-chat/BasicChatPageClient.js

@@ -891,7 +891,7 @@ export default function BasicChatPageClient() {
                         <div className="mb-3 grid grid-cols-2 gap-2 sm:grid-cols-3 mt-2">
                           {message.attachments.map((attachment) => (
                             <a key={attachment.id} href={attachment.dataUrl} target="_blank" rel="noreferrer" className="overflow-hidden rounded-[18px] border border-white/10 bg-black/20">
-                              <img src={attachment.dataUrl} alt={attachment.name} className="h-28 w-full object-cover" />
+                              <img src={attachment.dataUrl} alt={attachment.name} className="h-28 w-full object-cover" loading="lazy" decoding="async" />
                             </a>
                           ))}
                         </div>