feat(dashboard): send invitation emails on member invite

[johannmachemer]

Summary

• The member-invite route created the invitation row but never sent an email — sendEmail and renderInvitationEmail were dead code, so no invitee ever received a link.
• Wire them up: render the invitation template and send it, building the accept link as ${APP_URL}/invite/<token>.
• Response now returns emailSent; when SMTP is unconfigured it falls back to returning inviteUrl so an admin can still share the link manually (instead of always leaking the raw token).
• Forward SMTP_* vars to the dashboard container in docker-compose.yml (they were never passed through).
• Client toast reflects reality: success when sent, or a copyable invite link when email isn't configured.

Test plan

• With SMTP set, inviting a member delivers the email and the accept link works.
• Without SMTP, the invite still succeeds and the UI surfaces a copyable link.
• pnpm --filter @yavio/dashboard typecheck passes.

🤖 Generated with Claude Code

[github-actions]

Coverage Report for dashboard

Status	Category	Percentage	Covered / Total
🔵	Lines	84.26%	1392 / 1652
🔵	Statements	84.26%	1392 / 1652
🔵	Functions	88.88%	88 / 99
🔵	Branches	88.11%	267 / 303

File Coverage

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Generated in workflow #55 for commit fe1e351 by the Vitest Coverage Report Action