feat: playground static site with cursor webhook deploy

Scaffold nginx + deploy-hook stack for playground.schwenk.online,
Gitea cursor workflow, directory-based public/ content, and boka
bootstrap via git clone.

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

@@ -0,0 +1,13 @@
+# Copy to .env on boka — never commit .env
+
+# Gitea push webhook HMAC secret (same value in Gitea repo webhook settings)
+WEBHOOK_SECRET=change-me-to-a-long-random-string
+
+# Gitea deploy token (read repo) for git pull inside deploy-hook container
+DEPLOY_GIT_TOKEN=
+
+# Optional overrides
+# DEPLOY_BRANCH=main
+# DEPLOY_GIT_URL=https://gitea.schwenk.online/froxxxy/playground.git
+# HOST_UID=1002
+# HOST_GID=1002