Release 2026.8.0-rc3

See https://next.goauthentik.io/docs/releases/2026.8

What's Changed

• lib/sync/outgoing: allow discovery to be deactivated (cherry-pick #24667 to version-2026.8) by @authentik-cherry-pick[bot] in #24678
• website/docs: Mark the release notes for 2026.8 as 'beta' (cherry-pick #24682 to version-2026.8) by @authentik-cherry-pick[bot] in #24686
• ci: release tag: add validation that the workflow was started on the appropriate branch (cherry-pick #24676 to version-2026.8) by @authentik-cherry-pick[bot] in #24690
• web: hide plain action icons while loading (cherry-pick #24618 to version-2026.8) by @authentik-cherry-pick[bot] in #24688
• ci: release publish: fix missing gh cli env var by @rissson in #24695
• ci: release: rename major release to release family (cherry-pick #24691 to version-2026.8) by @authentik-cherry-pick[bot] in #24697

Full Changelog: version/2026.8.0-rc2...version/2026.8.0-rc3