chore: prepare repo for public release — scrub internal infra, rewrite README

- Remove owner-specific / legacy deploy files (home/prod/server compose, deploy/).
  The home compose stays as a local untracked file for the maintainer's own deploy.
- Genericise infra-specific code comments (egress-proxy examples) to neutral wording.
- Replace the hardcoded contact email on the legal pages with the instance operator's
  configured admin email, served via the public /auth/config and shown with a neutral
  fallback — so each self-hosted instance shows its own contact.
- Rewrite README for the current app + a copy-paste self-hosting quick start (prebuilt
  image + first-run wizard) with a build-from-source alternative; tidy .env.example.

frontend/src/components/legal/Terms.tsx

@@ -1,4 +1,4 @@
-import LegalLayout, { CONTACT_EMAIL, H2, LegalLink } from "./LegalLayout";
+import LegalLayout, { ContactEmail, H2, LegalLink } from "./LegalLayout";
 
 export default function Terms() {
   return (
@@ -56,11 +56,7 @@ export default function Terms() {
 
       <H2>Contact</H2>
       <p>
-        Questions:{" "}
-        <a href={`mailto:${CONTACT_EMAIL}`} className="text-accent hover:underline">
-          {CONTACT_EMAIL}
-        </a>
-        .
+        Questions: contact <ContactEmail />.
       </p>
     </LegalLayout>
   );