chore: clean up stale references and README

- jail.local: fix comment pointing to deleted docker-compose.cloudflare.yml
- .gitignore: remove .env entry (no env file in use)
- README: full rewrite to match current state (no .env, no webhook,
  correct file structure, inline compose config, CF setup instructions)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -1,9 +1,6 @@
 # Dependencies
 dashboard/node_modules/
 
-# Environment (contains secrets)
-.env
-
 # Runtime data
 data/
 *.json