feat(connections): revoke grant + public_repo + audit log + docs/privacy (PR-E)

[implemented.stream (thanabartbb)]

PR-E, the last one in the stack. Stacked on #21 (PR-D).

What

• Revoke: DELETE /api/connections/github calls DELETE /applications/{client_id}/grant (Basic auth with the OAuth app id/secret, token in body), then deletes the stored token. Deleting the account cascades to every 0010 table.
• Least privilege: /api/auth/github?scope=public requests read:user user:email public_repo. The callback now stores the scope GitHub actually granted (exchangeCodeWithScope).
• Audit log: GET /api/connections/audit (event types only) + list on /settings/connections.
• Docs:
  • docs/user-guide/customer-deploy.md (TH + EN): Cloudflare token template (Workers Scripts: Edit + Account Settings: Read), limits, deploy paths, self-heal, privacy note.
  • Design refs in docs/design/ui-ux-revamp-plan.md §16 (reference only, no copied code).
  • CHANGELOG Unreleased.
• Tests: tests/connections-revoke.test.ts.

Owner must do (whole stack A to E)

1. openssl rand -base64 32 → npx wrangler secret put CREDENTIALS_KEY, and keep an offline backup.
2. Review, then apply migration 0010_customer_connections.sql with npm run db:migrate:remote.
3. OAuth scope decision: keep repo as the default (private repos) or make public_repo the default. Both buttons exist; the default is repo. A GitHub App with per-repo installs is the long-term option.
4. Recommended: regenerate the OAuth client secret (it was seen once by tooling) and update GITHUB_CLIENT_SECRET.
5. Merge A → E in order, then approve a production deploy. Smoke-test direct deploy with a throwaway Cloudflare account first.
6. Decide pricing/limits (now 5 repos / 30 PRs / 20 deploys per user per day, 3 fix attempts).

Not merged, not deployed, no remote migration, no secrets set.

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