fix: skip password confirmation for OAuth users

OAuth users don't have passwords set, so they should not be prompted for password confirmation when performing destructive actions. This fix:
- Detects OAuth users via the hasPassword() method
- Skips password confirmation in modal for OAuth users
- Keeps text name confirmation as the final step
- Centralizes logic in helper functions for maintainability
- Changes button text to "Confirm" when password step is skipped

Fixes #4457

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

app/Models/User.php

@@ -443,4 +443,13 @@ class User extends Authenticatable implements SendsEmail
             && $this->email_change_code_expires_at
             && Carbon::now()->lessThan($this->email_change_code_expires_at);
     }
+
+    /**
+     * Check if the user has a password set.
+     * OAuth users are created without passwords.
+     */
+    public function hasPassword(): bool
+    {
+        return ! empty($this->password);
+    }
 }