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/config.py

@@ -66,8 +66,8 @@ class Settings(BaseSettings):
     # preferred for shared backfill/enrichment so it doesn't depend on a specific user.
     youtube_api_key: str = ""
     # Optional HTTP(S) proxy for outbound YouTube Data API calls. Set this to send the
-    # scheduler's googleapis traffic through a fixed-IP host (e.g. the VPS over WireGuard) so an
-    # IP-restricted API key keeps working even when this host's public IP is dynamic.
+    # scheduler's googleapis traffic through a fixed-IP host so an IP-restricted API key
+    # keeps working even when this host's public IP is dynamic.
     youtube_api_proxy: str = ""
     # Daily quota budget (units). Default leaves headroom under the 10,000/day free limit.
     quota_daily_budget: int = 9000