Add relay profile switching

src/features/posts/bird-client.server.ts

@@ -1,13 +1,17 @@
 import { TwitterClient } from '@yuta/bird'
 import type { BirdReader } from './post-service'
 
-let client: TwitterClient | undefined
+const clients = new Map<string | undefined, TwitterClient>()
 
-export function getBirdReader(): BirdReader {
-  client ??= new TwitterClient({
+export function getBirdReader(profileName?: string): BirdReader {
+  const existing = clients.get(profileName)
+  if (existing) return existing
+
+  const client = new TwitterClient({
     relayBaseUrl: process.env.TWITTER_RELAY_BASE_URL,
-    profileName: process.env.BIRD_PROFILE_NAME,
+    profileName,
     timeoutMs: 20_000,
   })
+  clients.set(profileName, client)
   return client
 }