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.

backend/app/youtube/client.py

@@ -44,8 +44,8 @@ class YouTubeClient:
     def __init__(self, db, user: User):
         self.db = db
         self.user = user
-        # Optionally route all YouTube traffic through a fixed-IP egress proxy (e.g. the VPS
-        # over WireGuard) so an IP-restricted API key keeps working from a dynamic-IP host.
+        # Optionally route all YouTube traffic through a fixed-IP egress proxy so an
+        # IP-restricted API key keeps working from a host with a dynamic public IP.
         proxy = sysconfig.get_str(db, "youtube_api_proxy") or None
         self._http = httpx.Client(timeout=30.0, proxy=proxy)