serve static assets from local public/ instead of static.officer.dev, simplify gmail history 404/410 handling

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/servers/queue/handlers/gmail-sync.ts

@@ -142,13 +142,8 @@ async function getHistoryChanges(
 
     const res = await gmailApiFetch(accessToken, '/history', params);
 
-    if (res.status === 404) {
-      // No history — nothing new
-      return { messageIds: [], historyId: latestHistoryId };
-    }
-
-    if (res.status === 410) {
-      // historyId too old — caller should fall back to date-based listing
+    if (res.status === 404 || res.status === 410) {
+      // historyId too old or invalid — caller should fall back to date-based listing
       throw new HistoryExpiredError();
     }