fix(config): secure-by-default loopback bind and startup-error logging

- Default `host: 127.0.0.1` in config.example.yaml; require explicit
  api_tokens or `allow_lan_without_auth: true` before binding LAN.
- Mirror pre-uvicorn fatal errors to startup-errors.log in the config
  dir so silent boot failures via wscript/pythonw are diagnosable.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

config.example.yaml

@@ -1,7 +1,13 @@
 # Media Server Configuration
 # Copy this file to config.yaml and customize as needed.
-# By default, authentication is DISABLED (no tokens = open access).
-# To enable auth, uncomment and configure the api_tokens section below.
+#
+# Secure-by-default: the server binds to loopback (127.0.0.1) only and refuses
+# to bind a non-loopback address with no tokens configured.
+#
+# To expose on the LAN you must do ONE of:
+#   1. Configure api_tokens below AND change host to "0.0.0.0", OR
+#   2. Set `allow_lan_without_auth: true` (LAN-open, no auth — insecure on
+#      hostile networks, only acceptable on a trusted home LAN).
 
 # API Tokens - Multiple tokens with friendly labels
 # This allows you to identify which client is making requests in the logs
@@ -11,8 +17,9 @@
 #   web_ui: "your-web-ui-token-here"
 
 # Server settings
-host: "0.0.0.0"
+host: "127.0.0.1"
 port: 8765
+# allow_lan_without_auth: true   # uncomment + change host to 0.0.0.0 for LAN-open mode
 
 # Custom scripts
 scripts: