[Feat] Add Stripe built-in integration

[roomote-roomote]

​Opened on behalf of @daniel-lxs. Follow up by mentioning @roomote-roomote, in the web UI, or in Telegram.

What changed

• Added Stripe to the existing MCP_INTEGRATIONS registry as a deployment-scoped hosted MCP connection backed by an encrypted restricted API key.
• Reused the existing Settings integration list and shared CredentialIntegrations.tsx flow used by admin-configured providers. This adds no new list, section, or special UI.
• Restricted credential input to rk_ keys while preserving blank edits that retain an existing stored key; unrestricted sk_* and public keys are rejected before persistence.
• Forwarded the restricted key only through the control-plane proxy, initialized stripe_api_write as disabled, and preserved admin Manage tools control for opt-in writes.
• Added the Simple Icons Stripe mark, self-setup and Slack recommendation metadata, Dashboard URL detection, task setup guidance, public docs, and focused registry, persistence, proxy-auth, schema, and Settings tests.

Why this change was made

Stripe's official hosted MCP server supports restricted API keys for persistent application access. The deployment-key model matches the researched shared-account scope while preventing accidental storage of unrestricted secret keys.

Impact

Operators can configure Stripe in the same built-in list as existing integrations. Keys are encrypted at rest, unrestricted secret keys are rejected, agent traffic receives only the Roomote proxy URL, and the general write tool starts disabled. Schema and Settings regressions passed alongside the existing proxy/persistence tests, full check-types, lint:fast, and git diff --check. Live Stripe authentication, sandbox reads, and credential-backed tool discovery were not performed.

Related PRs

• Cloudflare #2992
• CircleCI #2993
• Buildkite #2994

[roomote-community]

No new pull request changes since the prior reviewed commit; no code issues found. See task

• Restrict the Stripe credential schema to rk_ keys so unrestricted secret keys cannot be stored.

_{Reviewed d405ee3}