refactor: współdzielony LangSwitcher także w nagłówkach podstron

Przełącznik siedział w Header.tsx, który renderuje się tylko na landingu —
PrivacyPolicyPage i PlatformPage mają własne <header>. Z /en/privacy i
/en/platforma nie dało się wrócić na PL inaczej niż przez stronę główną
albo ręczną edycję URL-a.

Wyciągnięty do src/components/LangSwitcher.tsx i wstawiony w oba nagłówki
obok linku powrotnego.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/components/Header.tsx

@@ -1,39 +1,8 @@
 import React, { useState, useEffect } from 'react';
 import { Menu, X } from 'lucide-react';
 import { motion, AnimatePresence } from 'framer-motion';
-import { localizePath, setLang, useLang, type Lang } from '../i18n';
-
-const LANGS: Lang[] = ['pl', 'en'];
-
-// PL / EN toggle. Buttons rather than links: switching is a client-side
-// navigation (setLang), so a real href would reload the whole document.
-const LangSwitcher = ({ onSwitch }: { onSwitch?: () => void }) => {
-  const lang = useLang();
-
-  return (
-    <div className="flex items-center gap-2 text-sm font-medium" role="group" aria-label="Język / Language">
-      {LANGS.map((code, i) => (
-        <React.Fragment key={code}>
-          {i > 0 && <span aria-hidden="true" className="text-muted/40">/</span>}
-          <button
-            type="button"
-            lang={code}
-            aria-current={code === lang ? 'true' : undefined}
-            onClick={() => {
-              setLang(code);
-              onSwitch?.();
-            }}
-            className={`uppercase tracking-wide transition-colors ${
-              code === lang ? 'text-foreground' : 'text-muted hover:text-foreground'
-            }`}
-          >
-            {code}
-          </button>
-        </React.Fragment>
-      ))}
-    </div>
-  );
-};
+import { localizePath, useLang } from '../i18n';
+import LangSwitcher from './LangSwitcher';
 
 const Header = () => {
   const lang = useLang();

src/components/LangSwitcher.tsx

@@ -0,0 +1,44 @@
+import React from 'react';
+import { setLang, useLang, type Lang } from '../i18n';
+
+const LANGS: Lang[] = ['pl', 'en'];
+
+/**
+ * PL / EN toggle. Buttons rather than links: switching is a client-side
+ * navigation (setLang), so a real href would reload the whole document.
+ *
+ * Shared by the landing Header and the standalone pages' own headers — without
+ * it on those pages, /en/privacy and /en/platforma have no way back to Polish
+ * short of editing the URL.
+ *
+ * @param onSwitch runs after the language changes — used to close the mobile menu.
+ */
+const LangSwitcher = ({ onSwitch }: { onSwitch?: () => void }) => {
+  const lang = useLang();
+
+  return (
+    <div className="flex items-center gap-2 text-sm font-medium" role="group" aria-label="Język / Language">
+      {LANGS.map((code, i) => (
+        <React.Fragment key={code}>
+          {i > 0 && <span aria-hidden="true" className="text-muted/40">/</span>}
+          <button
+            type="button"
+            lang={code}
+            aria-current={code === lang ? 'true' : undefined}
+            onClick={() => {
+              setLang(code);
+              onSwitch?.();
+            }}
+            className={`uppercase tracking-wide transition-colors ${
+              code === lang ? 'text-foreground' : 'text-muted hover:text-foreground'
+            }`}
+          >
+            {code}
+          </button>
+        </React.Fragment>
+      ))}
+    </div>
+  );
+};
+
+export default LangSwitcher;

src/components/PlatformPage.tsx

@@ -2,6 +2,7 @@ import React from 'react';
 import { ArrowRight, Building2, CheckCircle2, ChevronRight, Home } from 'lucide-react';
 import Footer from './Footer';
 import { localizePath, useLang } from '../i18n';
+import LangSwitcher from './LangSwitcher';
 
 // Standalone product page at /platforma (and /en/platforma). The copy is not
 // localized yet — the site only translates contact.* and privacy.* — but the
@@ -16,9 +17,12 @@ const PlatformPage = () => {
           <a href={localizePath('/', lang)} className="text-2xl font-bold tracking-tight hover:opacity-80 transition-opacity">
             human<span className="text-primary">AI</span>
           </a>
+          <div className="flex items-center gap-6">
             <a href={localizePath('/', lang)} className="text-sm text-muted hover:text-foreground transition-colors">
               ← Wróć na stronę główną
             </a>
+            <LangSwitcher />
+          </div>
         </div>
       </header>
 

src/components/PrivacyPolicyPage.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { localizePath, useLang, useT } from '../i18n';
 import Footer from './Footer';
+import LangSwitcher from './LangSwitcher';
 
 const PrivacyPolicyPage = () => {
   const t = useT();
@@ -14,9 +15,12 @@ const PrivacyPolicyPage = () => {
           <a href={home} className="text-2xl font-bold tracking-tight hover:opacity-80 transition-opacity">
             human<span className="text-primary">AI</span>
           </a>
+          <div className="flex items-center gap-6">
             <a href={home} className="text-sm text-muted hover:text-foreground transition-colors">
               {t.privacy.backToHome}
             </a>
+            <LangSwitcher />
+          </div>
         </div>
       </header>