Fix Caddy startup: remove empty ACME_EMAIL that caused parse error

Caddy's email directive requires a non-empty argument. Since ACME_EMAIL
wasn't set, Caddy failed to parse the config. Email is optional for
Let's Encrypt — remove the directive entirely and document it as a
manual opt-in comment.

infra/.env.example

@@ -1,5 +1,5 @@
 # Your domain — apps will be served at <name>.yourdomain.com
 DOMAIN_SUFFIX=yourdomain.com
 
-# Email address for Let's Encrypt expiry notices (required for HTTPS)
-ACME_EMAIL=you@example.com
+# Optional: email for Let's Encrypt expiry notices.
+# If you want this, uncomment the `email` line in proxy/Caddyfile instead.

infra/docker-compose.yml

@@ -55,7 +55,6 @@ services:
       - "2019:2019"   # admin API
     environment:
       DOMAIN_SUFFIX: ${DOMAIN_SUFFIX:-localhost}
-      ACME_EMAIL: ${ACME_EMAIL:-}
     volumes:
       - ../proxy/Caddyfile:/etc/caddy/Caddyfile:ro
       - caddy-data:/data

proxy/Caddyfile

@@ -15,8 +15,8 @@
     # Admin API — used by hiy-server to add/remove app routes dynamically.
     admin 0.0.0.0:2019
 
-    # Contact email for Let's Encrypt expiry notices.
-    email {$ACME_EMAIL}
+    # Uncomment and set your email for Let's Encrypt expiry notices:
+    # email you@example.com
 }
 
 # HIY dashboard — served at your root domain.