Status email alerts, portal polish, and delete_tag API

Overnight ship batch:

• Status page email subscribers — public opt-in on /{slug}/status, incident create/update fan-out, settings subscriber counts (migration 0126).
• Portal fixes — hide Updates when changelog is off; hub section toggles gate primary nav; search changelog URLs + disabled-feed filtering; sitemap omits disabled surfaces; domain default host from env.
• Anonymous vote / prioritize on optional and anonymous projects (with verified-email still enforced when configured).
• Embed waits for auth before submit; composer sign-in link fixed.
• Support → feedback converts deep-link to the admin post page.
• API — delete_tag on MCP / REST / @hollahoop/sdk / OpenAPI.