chore(analytics): remove Freebuff ad tracking and the Beluga short-link rewrite - #9974

Summary

• Remove Freebuff ad tracking end to end: the consent-gated tag script, the signup conversion call, the server-side conversion postback in the user-create hook, the click-id cookie guard, the FREEBUFF_API_KEY env var, and both freebuff.com CSP origins
• Drop bfcid from the attribution click-id list
• Remove Freebuff from the cookie policy (cookie table, opt-out line, provider list) and the privacy policy (processing table, advertising section, opt-outs, CCPA disclosure), and bump both "Last updated" dates. Removing a provider narrows collection, so no re-consent prompt is needed
• Remove the /r/:shortCode rewrite to Beluga short links

Type of Change

• Chore

Testing

• Pure removal; repo-wide grep for freebuff, bfcid and beluga is empty
• biome on the changed files; type-check, audits and tests run in CI

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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