feat(docs): added footer for page navigation, i18n for docs (#1339)

* update infra and remove railway

* feat(docs): added footer for page navigation, i18n for docs

* Revert "update infra and remove railway"

This reverts commit abfa2f8d51.

* added SEO-related stuff

* fix image sizes

* add missing pages

* remove extraneous comments

apps/docs/components/ui/image.tsx

@@ -11,7 +11,7 @@ interface ImageProps extends Omit<NextImageProps, 'className'> {
 }
 
 export function Image({
-  className = 'w-full rounded-xl border border-border shadow-sm overflow-hidden',
+  className = 'w-full',
   enableLightbox = true,
   alt = '',
   src,
@@ -29,7 +29,7 @@ export function Image({
     <>
       <NextImage
         className={cn(
-          'object-cover',
+          'overflow-hidden rounded-xl border border-border object-cover shadow-sm',
           enableLightbox && 'cursor-pointer transition-opacity hover:opacity-90',
           className
         )}

apps/docs/components/ui/language-dropdown.tsx

@@ -0,0 +1,107 @@
+'use client'
+
+import { useEffect, useState } from 'react'
+import { Check, ChevronDown } from 'lucide-react'
+import { useParams, usePathname } from 'next/navigation'
+
+const languages = {
+  en: { name: 'English', flag: '🇺🇸' },
+  es: { name: 'Español', flag: '🇪🇸' },
+  fr: { name: 'Français', flag: '🇫🇷' },
+  zh: { name: '简体中文', flag: '🇨🇳' },
+}
+
+export function LanguageDropdown() {
+  const [isOpen, setIsOpen] = useState(false)
+  const pathname = usePathname()
+  const params = useParams()
+
+  const [currentLang, setCurrentLang] = useState(() => {
+    const langFromParams = params?.lang as string
+    return langFromParams && Object.keys(languages).includes(langFromParams) ? langFromParams : 'en'
+  })
+
+  useEffect(() => {
+    const langFromParams = params?.lang as string
+
+    if (langFromParams && Object.keys(languages).includes(langFromParams)) {
+      if (langFromParams !== currentLang) {
+        setCurrentLang(langFromParams)
+      }
+    } else {
+      if (currentLang !== 'en') {
+        setCurrentLang('en')
+      }
+    }
+  }, [params, currentLang])
+
+  const handleLanguageChange = (locale: string) => {
+    if (locale === currentLang) {
+      setIsOpen(false)
+      return
+    }
+
+    setIsOpen(false)
+
+    const segments = pathname.split('/').filter(Boolean)
+
+    if (segments[0] && Object.keys(languages).includes(segments[0])) {
+      segments.shift()
+    }
+
+    let newPath = ''
+    if (locale === 'en') {
+      newPath = segments.length > 0 ? `/${segments.join('/')}` : '/introduction'
+    } else {
+      newPath = `/${locale}${segments.length > 0 ? `/${segments.join('/')}` : '/introduction'}`
+    }
+
+    window.location.href = newPath
+  }
+
+  return (
+    <div className='relative'>
+      <button
+        onClick={(e) => {
+          e.preventDefault()
+          e.stopPropagation()
+          setIsOpen(!isOpen)
+        }}
+        className='flex items-center gap-2 rounded-xl border border-border/20 bg-muted/50 px-3 py-2 text-sm backdrop-blur-sm transition-colors hover:bg-muted'
+      >
+        <span className='text-base'>{languages[currentLang as keyof typeof languages]?.flag}</span>
+        <span className='font-medium text-foreground'>
+          {languages[currentLang as keyof typeof languages]?.name}
+        </span>
+        <ChevronDown
+          className={`h-3 w-3 text-muted-foreground transition-transform ${isOpen ? 'rotate-180' : ''}`}
+        />
+      </button>
+
+      {isOpen && (
+        <>
+          <div className='fixed inset-0 z-10' onClick={() => setIsOpen(false)} />
+          <div className='absolute top-full left-0 z-20 mt-1 w-48 rounded-lg border border-border/50 bg-background/95 shadow-xl backdrop-blur-md'>
+            {Object.entries(languages).map(([code, lang]) => (
+              <button
+                key={code}
+                onClick={(e) => {
+                  e.preventDefault()
+                  e.stopPropagation()
+                  handleLanguageChange(code)
+                }}
+                className={`flex w-full items-center gap-3 px-3 py-2.5 text-sm transition-colors first:rounded-t-lg last:rounded-b-lg hover:bg-muted/80 ${
+                  currentLang === code ? 'bg-muted/60 font-medium text-primary' : 'text-foreground'
+                }`}
+              >
+                <span className='text-base'>{lang.flag}</span>
+                <span>{lang.name}</span>
+                {currentLang === code && <Check className='ml-auto h-4 w-4 text-primary' />}
+              </button>
+            ))}
+          </div>
+        </>
+      )}
+    </div>
+  )
+}