docs: correct credential profile sync and add a security policy

[datlechin]

Why

The iCloud Sync and Credential Profiles pages said credential profiles do not sync yet. They have synced between Macs since 0.75.0. The repository had no security policy, the code of conduct listed a personal address, and the three build guides named three different macOS versions, none of which runs Xcode 26.

Change

• Credential profiles: both pages and the FAQ say what crosses (name, username, where the password comes from) and what stays on each Mac (the password unless Passwords is on, and which connections use the profile).
• SECURITY.md: report by email, what to include, what is in scope, and that only the latest release gets fixes.
• CODE_OF_CONDUCT.md: the contact is hello@tablepro.app.
• README.md, README.ko.md and CONTRIBUTING.md: the build needs Xcode 26, with no separate macOS number.

Verified

mint validate, mint broken-links --check-anchors --check-redirects, mint a11y and the three scripts under docs/scripts pass. Docs only, so no test.

Not in this PR

• GitHub private vulnerability reporting is off for this repository, so SECURITY.md names email only.

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Project	Status	Preview	Updated
TablePro	🟢 Ready	View Preview	Oct 8, 2026, 4:19 PM

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