MCP `email_verify`: the caller asks for a new verification email, with the same limits as the API #4834

Intent: an agent signing its person up can get the verification email sent again without a page.

Done:

• [ ] src/http/mcp.ts has an email_verify tool, placed right after signup, with no input. It calls what POST /api/v1/user/email/verify calls, for the caller only, with the same rate limit and the same answer
• [ ] the answer never contains the verification link or token
• [ ] docs/MCP.md has its row beside signup
• [ ] test/mcp-email-verify.test.ts: an unverified person asks and one email is queued (use the test mailer the API's own tests use); asking again inside the limit is refused like the API refuses; a verified person is told so

Risks: test/mcp-size.test.ts holds tools/list under a 37,000-byte headroom, so keep the description short. #4795 also places a tool right after signup: if it has landed, place this one right after ssh_keys instead.