feat: fix multi-part archive forwarding and add kickstarter package linking

Multi-part send fix:
- Add destMessageIds BigInt[] to Package schema with backfill migration
- Worker uploadToChannel now returns all message IDs, stored in DB
- Bot forwards all parts of multi-part archives (not just the first)
- Add retry logic for upload rate limits (429) and download stalls

Kickstarter package linking:
- Add package search/linking queries and API routes
- Add PackageLinkerDialog with search + checkbox selection
- Add "Link Packages" and "Send All" actions to kickstarter table
- Add sendAllKickstarterPackages server action

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bot/src/tdlib/client.ts

@@ -121,6 +121,25 @@ export async function copyMessageToUser(
   }, fileName);
 }
 
+/**
+ * Send multiple document messages from a channel to a user's DM.
+ * Used for multi-part archives where each part is a separate Telegram message.
+ * Sends parts sequentially with a small delay to avoid rate limits.
+ */
+export async function copyMultipleMessagesToUser(
+  fromChatId: bigint,
+  messageIds: bigint[],
+  toUserId: bigint
+): Promise<void> {
+  for (let i = 0; i < messageIds.length; i++) {
+    await copyMessageToUser(fromChatId, messageIds[i], toUserId);
+    // Small delay between parts to avoid rate limits
+    if (i < messageIds.length - 1) {
+      await new Promise((resolve) => setTimeout(resolve, 1000));
+    }
+  }
+}
+
 /**
  * Send a message and wait for Telegram to confirm delivery.
  * Returns when updateMessageSendSucceeded fires for the temp message.