chore: stop tracking apps/coder/.env.host

Untrack the host env file (git rm --cached, kept on disk for the boocoder
service) and widen .gitignore to .env.* (re-including .env.example) so env
files no longer get committed. The file's prior contents (dev DB password +
internal Tailscale URLs; no API keys) remain in history — left as-is given the
single-user Tailscale-only threat model.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,8 @@
 node_modules
 dist
 .env
+.env.*
+!.env.example
 
 # Claude / Cursor (local agent & IDE config — CLAUDE.md and AGENTS.md stay tracked)
 .claude/