chore(release): v0.1.0-beta.8

[ABB65]

Release v0.1.0-beta.8

Version bump + changelog for the next prerelease (continues the 0.1.0-beta.* line; previous tag v0.1.0-beta.7, 2026-04-13).

This is the release commit only — package.json → 0.1.0-beta.8 and the generated CHANGELOG.md section. No app code changes.

What's in this cut (since v0.1.0-beta.7)

24 features · 28 fixes · 1 perf — highlights:

• Billing/Polar: payment_accounts + usage outbox, Polar plugin + meters, paywall/trial UX, overage billing, trial reminder emails
• MCP Cloud: hosted HTTP endpoint + key management, tool allowlist, quota semantics, workflow/plan-aware external writes
• Open core: deployment profiles + edition-aware license system, editions/licensing surface, edition-aware UI
• GitHub App: repo-level access lifecycle (revoke/delete/rename), connect-existing flow
• This session's fixes: chat trace persistence (fix(chat): persist conversation trace rows reliably #59), document slug validation (fix(content): validate document slug passed as a separate argument #60), MCP Cloud reachability — session-middleware exemptions for /api/mcp, /api/forms, /api/conversation (fix(mcp-cloud): exempt /api/mcp from the session auth middleware #61, fix(auth): exempt forms + conversation API from session middleware #62) + proxy Accept-header forwarding (fix(mcp-cloud): forward client Accept header to the loopback MCP server #64)

Release process (after this PR merges)

Per docs/RELEASING.md, once merged to main:

1. Tag the merged commit: git tag v0.1.0-beta.8 && git push origin v0.1.0-beta.8
2. release.yml validates package.json == tag, runs the full gate (lint, typecheck, test:ci, test:rls, e2e, build), builds + pushes the Docker image to ghcr.io/contentrain/studio, and publishes a GitHub prerelease.

Staging (this exact main HEAD) already verified: auth, chat round-trip, forms, and full MCP Cloud CRUD.