feat: add Russian localization and independent STT languages

app/api/chats/[id]/markdown/route.ts

@@ -11,14 +11,14 @@
  * markers are invisible by the engine's law).
  */
 import { sessionMarkdown } from "@/src/core";
-import { getChat } from "@/src/server";
+import { getChat, applicationLanguage } from "@/src/server";
 
 /** Filename-safe title (own module scope on purpose: tiny + pure). */
 function slugify(title: string): string {
 	const slug = title
 		.toLowerCase()
 		.normalize("NFKD")
-		.replace(/[^a-z0-9]+/g, "-")
+		.replace(/[^\p{L}\p{N}]+/gu, "-")
 		.replace(/^-+|-+$/g, "");
 	return slug.length > 0 ? slug : "session";
 }
@@ -27,11 +27,11 @@ export async function GET(_req: Request, ctx: { params: Promise<{ id: string }>
 	const { id } = await ctx.params;
 	const record = getChat(id);
 	if (!record) return Response.json({ error: "Unknown chat" }, { status: 404 });
-	const markdown = sessionMarkdown(record.messages, { title: record.title, anchors: false });
+	const markdown = sessionMarkdown(record.messages, { title: record.title, anchors: false, language: applicationLanguage(_req.headers.get("accept-language")) });
 	return new Response(markdown, {
 		headers: {
 			"content-type": "text/markdown; charset=utf-8",
-			"content-disposition": `attachment; filename="${slugify(record.title)}.md"`,
+			"content-disposition": `attachment; filename="${/^[a-z0-9-]+$/.test(slugify(record.title)) ? slugify(record.title) : "session"}.md"; filename*=UTF-8''${encodeURIComponent(slugify(record.title))}.md`,
 		},
 	});
 }