Add Dynamic DNS (DynDNS2 listener + domain UI)

Imported from GitHub pull request El-SaMa/oma#119 by @El-SaMa.

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Summary

• DynDNS2 listener at /api/ddns/nic/update updates live A/AAAA via Cloudflare, Enhance, or cPanel ZoneEdit
• Domain manage tab, DNS card, searchable host list, token mint/rotate; migration 0088_ddns.sql
• Platform/MCP tools (oma.list_ddns_hosts, create/rotate/delete), unit + listener contract tests, admin docs with draw.io flow and data-model charts

Test plan

• Apply migration 0088_ddns.sql
• pnpm --dir services/core-api test -- src/ddns/ddns.test.ts
• pnpm --dir apps/web exec vitest run lib/ddns/listener.test.ts
• Create a DDNS host under Domain manage → Dynamic DNS; copy token
• curl DynDNS update with hostname + token → good then nochg
• Confirm A record updated; check Admin Docs → Dynamic DNS diagrams