add yml config file, client now does not depends on .env

.env.example

@@ -1,5 +1,5 @@
-# nexus-sync environment example
-# Copy this file to .env and replace example secrets before running.
+# nexus-sync server environment example
+# Copy this file to .env and replace example secrets before running the server.
 
 # -----------------------------------------------------------------------------
 # Server configuration
@@ -15,33 +15,5 @@
 # better to set this explicitly.
 NEXUS_SYNC_CLIENT_TOKENS="dev-client:dev-token"
 
-# Logging level for both server and client: DEBUG, INFO, WARNING, ERROR, CRITICAL.
+# Logging level for the server: DEBUG, INFO, WARNING, ERROR, CRITICAL.
 NEXUS_SYNC_LOG_LEVEL="INFO"
-
-# -----------------------------------------------------------------------------
-# Client configuration
-# -----------------------------------------------------------------------------
-
-# Base URL of the nexus-sync server.
-NEXUS_SYNC_SERVER_URL="http://127.0.0.1:8000"
-
-# Stable ID of this machine/client. Must match one client_id from
-# NEXUS_SYNC_CLIENT_TOKENS on the server.
-NEXUS_SYNC_CLIENT_ID="dev-client"
-
-# Bearer token for this client. Must match the token paired with
-# NEXUS_SYNC_CLIENT_ID on the server.
-NEXUS_SYNC_CLIENT_TOKEN="dev-token"
-
-# Commands this client is allowed to execute when the server requests them.
-# Supported presets currently implemented:
-#   - hostname
-#   - network_interfaces
-#
-# Safer explicit allowlist:
-NEXUS_SYNC_ALLOWED_COMMANDS="hostname,network_interfaces"
-
-# Alternative: allow every locally registered preset. This still does NOT allow
-# arbitrary shell strings from the server. Uncomment instead of the line above if
-# desired.
-# NEXUS_SYNC_ALLOWED_COMMANDS="full_access"