Fix multiple user panel 500 errors

- domains: VhostManager::create() called with array instead of 4 params
- PHPManager: VhostManager not required; pool writes use sudo tee (permission);
  updateConfig creates pool if missing instead of throwing
- DatabaseManager: MySQL ops used SQLite panel PDO; add dedicated mysqlPdo()
  using MariaDB socket auth
- BackupManager: column name is size_mb not size; diskUsage returns float
- DB.php: add LAST_INSERT_ID() → last_insert_rowid() translation
- user.js: SSL issue/submit used Nova.api (JSON) but endpoint streams SSE;
  add _sslStream() helper matching admin panel behavior
- schema/migration: add enc_password column to email_accounts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

panel/lib/DB.php

@@ -93,6 +93,9 @@ class DB {
             $sql
         );
 
+        // LAST_INSERT_ID() → last_insert_rowid()
+        $sql = preg_replace('/\bLAST_INSERT_ID\(\)/i', 'last_insert_rowid()', $sql);
+
         // IFNULL → COALESCE (SQLite supports both but be safe)
         $sql = preg_replace('/\bIFNULL\s*\(/i', 'COALESCE(', $sql);