contrib: remove Bitcoin/upstream-only files, adapt systemd and daemontools to Palladium

Removed: Dockerfile_beefyserver (superseded by the root Dockerfile), sdist/
(upstream release tooling), query.py (broken debug script), raspberrypi3/
(obsolete distro steps and env vars the server now rejects).

systemd and daemontools samples now use COIN=Palladium, the node RPC port 2332,
DB_ENGINE and SERVICES (both required for a working server). HOWTO.rst drops
the Raspberry Pi section.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

contrib/systemd/electrumx.conf

@@ -1,11 +1,17 @@
-# default /etc/electrumx.conf for systemd
+# default /etc/electrumx.conf for systemd (plm-electrumx, Palladium)
 
 # REQUIRED
 DB_DIRECTORY = /db
-# Bitcoin Node RPC Credentials
-DAEMON_URL = http://username:password@hostname:port/
+# leveldb or rocksdb (the matching pip extra must be installed)
+DB_ENGINE = rocksdb
+# Palladium node RPC credentials (the node needs server=1 and txindex=1)
+DAEMON_URL = http://username:password@127.0.0.1:2332/
+# without SERVICES the server accepts no connections. rpc:// is needed by electrumx_rpc (used by the service file to stop)
+SERVICES = tcp://:50001,rpc://
 
-# COIN = Bitcoin
+# Palladium is the default coin; NET can be mainnet (default), testnet or regtest
+# COIN = Palladium
+# NET = mainnet
 
-# See https://electrumx-spesmilo.readthedocs.io/en/latest/environment.html for
-# information about other configuration settings you probably want to consider.
+# See docs/environment.rst for information about other configuration settings
+# you probably want to consider (SSL_CERTFILE/SSL_KEYFILE and ssl:// in SERVICES, REPORT_SERVICES, ...).