feat: reuse tabs across multi-run — no more tab bloat

- tabRegistry preserved across resetState (like seenCodes/accounts)
- New reuseOrCreateTab() helper: navigates existing tab or creates new one
- All steps use reuseOrCreateTab: VPS panel, auth page, mail
- Mail tabs: only activate if alive, don't re-navigate (preserves session)
- Auth tab: reused between step 2→6→8, navigated to new URLs
- VPS tab: reused across runs, re-injected on navigation

content/chatgpt.js

@@ -39,7 +39,7 @@ async function step6_loginChatGPT() {
   // Get state for email and password
   const state = await chrome.runtime.sendMessage({ type: 'GET_STATE' });
   const email = state.email;
-  const password = state.password || 'mimashisha0.0';
+  const password = state.password;
 
   if (!email) throw new Error('No email found in state. Complete earlier steps first.');