fix(route/telegram): pass media range limit to iterDownload in bytes (#23672)

* fix(route/telegram): pass media range limit to iterDownload in bytes

iterDownload counts limit in bytes, but streamDocument passed the number
of 512 KiB blocks. Every Range request therefore stopped after a single
block while Content-Length promised the whole range, so players stalled
and retried on each seek.

* fix: ignore HEAD instead of holding download slot

---------

lib/routes/telegram/channel-media.ts

@@ -95,7 +95,7 @@ async function* streamDocument(client: TelegramClient, obj: Api.Document, thumbS
             requestSize,
             dcId: obj.dcId,
             offset: alignedOffset,
-            limit: limit ? Math.ceil(limit.subtract(alignedOffset).add(1).toJSNumber() / requestSize) : undefined,
+            limit: limit ? limit.subtract(alignedOffset).add(1).toJSNumber() : undefined,
         }
     );
     for await (const chunk of chunks) {
@@ -166,6 +166,9 @@ export async function configureMiddlewares(ctx: Context) {
     }
 }
 function streamResponse(c: Context, bodyIter: AsyncGenerator<Buffer>) {
+    if (c.req.method === 'HEAD') {
+        return c.body(null);
+    }
     return stream(c, async (stream) => {
         let aborted = false;
         stream.onAbort(() => {