[Replacement] Add password manager endpoint hardening guide

[DicksonWu654]

Reviewable replacement for #419.

This branch preserves the pre-force-push review history and adds the latest fixes as forward merge history so the diff is easier to review.

[github-actions]

Sidebar Configuration Reminder

This PR includes added, renamed, or removed documentation files:

• docs/pages/guides/endpoint-security/password-manager-endpoint-hardening.mdx (added)

Please ensure that:

• The sidebar in vocs.config.tsx has been updated to include these files
• New content has the dev: true parameter so it's marked as under development
• Sidebar links match the file paths - use the preview deployment to verify

See Contributing Guide – Sidebar & Navigation for more details.

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_{This is an automated reminder. If this PR doesn't need sidebar changes, you can ignore this message.}

[DicksonWu654]

Closing this replacement PR. The original PR branch has been updated to include the same review-preserving merge history, so review can continue there.