Add brand logo + favicon across app surfaces

Ship the Podcast Distribution AI wordmark as real assets and replace the
Mic-tile + text placeholder everywhere it appeared.

- public/logo-dark.png (dark wordmark, for light backgrounds) and
  public/logo-light.png (light wordmark, for dark backgrounds)
- New <Logo> component swaps the two via Tailwind dark: variants, so the
  dark logo shows on all non-themed surfaces (marketing, auth, admin,
  public share) and the light logo only in dark-mode app surfaces
- Wire <Logo> into the marketing header/footer, auth layout, app header
  (default branch only - white-label org logos untouched), admin header
  (+ Admin badge), and the public share page
- Favicon via App Router file convention: app/icon.png + app/apple-icon.png

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/(public)/p/[shareId]/page.tsx

@@ -7,6 +7,7 @@ import { getActiveBranding, hexToHslTriplet } from "@/lib/branding";
 import { WaveformPlayer } from "@/components/app/waveform-player";
 import { Card, CardContent } from "@/components/ui/card";
 import { Badge } from "@/components/ui/badge";
+import { Logo } from "@/components/ui/logo";
 import type { StructuredScript } from "@/lib/ai/types";
 
 export const dynamic = "force-dynamic";
@@ -70,14 +71,14 @@ export default async function PublicSharePage({
       {/* Header / brand wordmark */}
       <header className="mb-8 flex items-center gap-2.5">
         {branding?.logoUrl ? (
-          // eslint-disable-next-line @next/next/no-img-element
-          <img src={branding.logoUrl} alt={brandName} className="h-7 w-auto" />
+          <>
+            {/* eslint-disable-next-line @next/next/no-img-element */}
+            <img src={branding.logoUrl} alt={brandName} className="h-7 w-auto" />
+            <span className="font-display text-base font-extrabold tracking-tight">{brandName}</span>
+          </>
         ) : (
-          <span className="flex h-8 w-8 items-center justify-center rounded-2xl bg-brand text-brand-foreground">
-            <Mic2 className="h-4 w-4" />
-          </span>
+          <Logo className="h-7 w-auto" />
         )}
-        <span className="font-display text-base font-extrabold tracking-tight">{brandName}</span>
       </header>
 
       <article className="space-y-8">