Update Caddyfile and docker-compose.yml for local development configuration

- Added global options in Caddyfile to disable automatic HTTPS and use local certificates.
- Updated docker-compose.yml to fallback to localhost for DOMAIN_NAME if not set, and removed unnecessary port mappings for HTTP/3.

docs/Caddyfile

@@ -1,5 +1,11 @@
 # Caddyfile for docs
-{$DOMAIN_NAME} {
+{
+    # Global options
+    auto_https off      # Disable automatic HTTPS
+    local_certs         # Use local certificates for development
+}
+
+{$DOMAIN_NAME:localhost} {
     # Enable compression
     encode zstd gzip
 
@@ -10,7 +16,6 @@
 
     # Security headers
     header {
-        Strict-Transport-Security max-age=31536000;
         X-Content-Type-Options nosniff
         X-Frame-Options DENY
         Referrer-Policy strict-origin-when-cross-origin