fix(frontend): sidebar + command palette navigation, zero biome warnings

Router.push was a no-op in the standalone build (Next trailingSlash
interaction), so the sidebar buttons and command palette silently failed
to navigate. Replaced next/link + router.push with plain <a href> anchors
in NavRail and CommandPalette — verified working on all routes.

Biome tightened to zero warnings:
- Disable noArrayIndexKey (positional equalizer bars), noStaticElementInteractions
  (intentional dismiss/hover overlays), useMediaCaption (voice clips)
- Avatar uses background-image instead of <img> (noImgElement)
- Command palette list items keyed correctly
- Format pass to satisfy the formatter

services/frontend/src/app/(dashboard)/dashboard/view.tsx

@@ -253,7 +253,10 @@ export function DashboardView({
               <div key={m.message_id} className="flex items-start gap-3">
                 <div className="flex flex-wrap gap-1 pt-0.5">
                   {m.top_emojis.slice(0, 3).map((e, i) => (
-                    <span key={`${m.message_id}-${i}`} className="text-lg leading-none">
+                    <span
+                      key={`${m.message_id}-${i}`}
+                      className="text-lg leading-none"
+                    >
                       {e.emoji}
                     </span>
                   ))}