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.

docker-compose.localdev.yml

@@ -46,7 +46,7 @@ services:
     depends_on:
       db:
         condition: service_healthy
-    # Harmless on Docker Desktop; needed if ever run under Docker-in-LXC.
+    # Harmless on Docker Desktop; needed on some nested/hardened Docker hosts.
     security_opt:
       - apparmor:unconfined
     ports: