feat: Add Russian i18n translations and fix CORS + API endpoint issues

- Implemented full Russian translation (ru) for 8 major pages
- Added LanguageSwitcher component with language detection
- Translated: Navigation, Settings, Workflows, Credentials, Banner, Examples
- Fixed API endpoint path: changed to use sans-api-v1 client for /v1/ endpoints
- Fixed CORS: added http://localhost:8081 to ALLOWED_ORIGINS
- Added locales infrastructure with i18next and react-i18next
- Created bilingual JSON files (en/ru) for 4 namespaces
- 220+ translation keys implemented
- Backend CORS configuration updated in .env
- Documentation: I18N implementation guides and installation docs

skyvern-frontend/src/routes/root/SideNav.tsx

@@ -9,9 +9,11 @@ import {
   LightningBoltIcon,
 } from "@radix-ui/react-icons";
 import { KeyIcon } from "@/components/icons/KeyIcon.tsx";
+import { useTranslation } from "react-i18next";
 
 function SideNav() {
   const { collapsed } = useSidebarStore();
+  const { t } = useTranslation("common");
 
   return (
     <nav
@@ -20,40 +22,40 @@ function SideNav() {
       })}
     >
       <NavLinkGroup
-        title="Build"
+        title={t("nav.build")}
         links={[
           {
-            label: "Discover",
+            label: t("nav.discover"),
             to: "/discover",
             icon: <CompassIcon className="size-6" />,
           },
           {
-            label: "Workflows",
+            label: t("nav.workflows"),
             to: "/workflows",
             icon: <LightningBoltIcon className="size-6" />,
           },
           {
-            label: "Runs",
+            label: t("nav.runs"),
             to: "/runs",
             icon: <CounterClockwiseClockIcon className="size-6" />,
           },
           {
-            label: "Browsers",
+            label: t("nav.browsers"),
             to: "/browser-sessions",
             icon: <GlobeIcon className="size-6" />,
           },
         ]}
       />
       <NavLinkGroup
-        title={"General"}
+        title={t("nav.general")}
         links={[
           {
-            label: "Settings",
+            label: t("nav.settings"),
             to: "/settings",
             icon: <GearIcon className="size-6" />,
           },
           {
-            label: "Credentials",
+            label: t("nav.credentials"),
             to: "/credentials",
             icon: <KeyIcon className="size-6" />,
           },