Initial release: procd service and LuCI app for copyparty

OpenWrt procd service script and LuCI JavaScript interface for
copyparty (https://github.com/9001/copyparty), a self-hosted file
sharing server.

Features:
- procd service with UCI-driven volumes, accounts, and TLS cert
- LuCI view: settings, volume/account grids, live status + start/stop
- ACME TLS support via combined key+fullchain PEM (--cert flag)
- Auto-respawn and reload-on-config-change via service_triggers

etc/config/copyparty

@@ -0,0 +1,17 @@
+config copyparty 'config'
+	option enabled '0'
+	option port '3923'
+	option name 'OWRT-NAS'
+	option script '/mnt/raid/copyparty-en.py'
+	option usernames '0'
+
+# Example volume:
+# config volume
+# 	option src '/mnt/raid/files'
+# 	option dst '/files'
+# 	option flags 'r'
+
+# Example account:
+# config account
+# 	option user 'alice'
+# 	option pass 'secret'