feat(tema): açık / koyu / sistem teması

- TemaSaglayici (next-themes) + alt bilgide TemaSecici
- globals.css: .dark bloğunda palet token'ları çevrilir; bileşenlere
  dark: sınıfı yazılmaz
- yüzeyler bg-white → bg-card, koyu haplar text-slate-50, SVG'lerde
  sabit renk yerine değişken
- DESIGN.md §2.3 + tasarim-denetim kuralları (yuzey-beyaz,
  koyu-hap-beyaz-yazi, dark-sinif), AGENTS.md karanlık mod bölümü
- docs: koyu tema denetimi raporu

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/features/katalog/components/tur-icerik.tsx

@@ -139,13 +139,13 @@ export function TurIcerik({ tur }: { tur: TurSlug }) {
             </h1>
             {/* Kimlik hapları (§4.12): tür + öteki türe geçiş */}
             <p className="mt-5 flex flex-wrap items-center justify-center gap-2 lg:justify-start">
-              <span className="inline-flex h-10 items-center gap-2 rounded-full border border-slate-200 bg-white px-4 text-sm font-semibold text-slate-800">
+              <span className="inline-flex h-10 items-center gap-2 rounded-full border border-slate-200 bg-card px-4 text-sm font-semibold text-slate-800">
                 <Ikon className="size-4 text-primary" aria-hidden />
                 {tur === "devlet" ? "Devlet" : "Vakıf"}
               </span>
               <Link
                 href={`/universiteler/${digerTur.slug}`}
-                className="inline-flex h-10 items-center gap-2 rounded-full border border-slate-200 bg-white px-4 text-sm font-semibold text-slate-800 transition-[background-color,border-color,color,transform] duration-150 hover:border-orange-500 hover:bg-orange-50/60 hover:text-orange-500 active:scale-[0.97]"
+                className="inline-flex h-10 items-center gap-2 rounded-full border border-slate-200 bg-card px-4 text-sm font-semibold text-slate-800 transition-[background-color,border-color,color,transform] duration-150 hover:border-orange-500 hover:bg-orange-50/60 hover:text-orange-500 active:scale-[0.97]"
               >
                 <DigerIkon className="size-4 text-primary" aria-hidden />
                 {digerTur.ad}
@@ -213,7 +213,7 @@ export function TurIcerik({ tur }: { tur: TurSlug }) {
             <li key={s.il}>
               <a
                 href={`#sehir-${turkishSlugify(s.il)}`}
-                className="inline-flex h-10 cursor-pointer items-center gap-1.5 rounded-full border border-slate-200 bg-white px-3.5 text-sm font-semibold text-slate-700 transition-[background-color,border-color,color,transform] duration-150 hover:border-orange-500 hover:bg-orange-50/60 hover:text-orange-500 active:scale-[0.97]"
+                className="inline-flex h-10 cursor-pointer items-center gap-1.5 rounded-full border border-slate-200 bg-card px-3.5 text-sm font-semibold text-slate-700 transition-[background-color,border-color,color,transform] duration-150 hover:border-orange-500 hover:bg-orange-50/60 hover:text-orange-500 active:scale-[0.97]"
               >
                 {s.ad}
                 <span className="font-normal tabular-nums text-slate-400">