perf(worker): run startup upload-recovery batches with bounded concurrency

Telegram soft-throttles sustained sequential getMessages calls from a
user account with growing per-call latency (no FLOOD_WAIT, so our retry
wrapper never sees it). On a large package count this made the
once-per-startup destination-message verification pass take 90+ minutes
and block the scheduler/fetch-listener from starting. Running up to 3
batches concurrently cuts wall-clock time well under real per-account
rate limits.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JMm2E4ecmATJo8HuBx92NP

worker/src/recovery.ts

@@ -84,15 +84,26 @@ export async function recoverIncompleteUploads(): Promise<void> {
     // Batch size for getMessages. TDLib accepts up to ~100 IDs per call.
     // Using 100 means 20k packages → ~200 round-trips instead of 20k.
     const BATCH_SIZE = 100;
+    // Telegram soft-throttles sustained sequential history reads from user
+    // accounts — no FLOOD_WAIT, just growing per-call latency the longer a
+    // single in-flight request stream runs. A small number of batches in
+    // flight at once cuts wall-clock time substantially without approaching
+    // real per-account rate limits.
+    const CONCURRENCY = 3;
 
+    const tdlibClient = client;
+    const destChannelInfo = destChannel;
+    const batches: (typeof packages)[] = [];
     for (const [, channelPackages] of byChannel) {
-      // Group packages by destChannelId (already done) — within each group,
-      // process in batches via getMessages (plural).
       for (let i = 0; i < channelPackages.length; i += BATCH_SIZE) {
-        const batch = channelPackages.slice(i, i + BATCH_SIZE);
+        batches.push(channelPackages.slice(i, i + BATCH_SIZE));
+      }
+    }
+
+    async function processBatch(batch: typeof packages) {
       const batchResults = await verifyMessagesBatch(
-          client,
-          destChannel.telegramId,
+        tdlibClient,
+        destChannelInfo.telegramId,
         batch.map((p) => p.destMessageId!)
       );
 
@@ -143,7 +154,17 @@ export async function recoverIncompleteUploads(): Promise<void> {
         }
       }
     }
+
+    let nextBatchIndex = 0;
+    async function poolWorker() {
+      while (nextBatchIndex < batches.length) {
+        const batch = batches[nextBatchIndex++];
+        await processBatch(batch);
       }
+    }
+    await Promise.all(
+      Array.from({ length: Math.min(CONCURRENCY, batches.length) }, () => poolWorker())
+    );
 
     log.info(
       {