fix(site): privacy@, legal@, support@ contacts

[rclanan]

Routes each contact to its mailbox (all confirmed to exist):

• privacy@: privacy page (cloud data + policy questions), trust page data export/erasure, contact page.
• legal@: trust page Legal & agreements card, contact page.
• support@: new Support card on the contact page; JSON-LD technical support contactPoint now has email support@ alongside the GitHub issues URL.
• security@ kept for vulnerability reports only.
• llms.txt contact section lists all mailboxes.

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