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Removed: Dockerfile_beefyserver (superseded by the root Dockerfile), sdist/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/daemontools/env/COIN

@@ -1 +1 @@
-Bitcoin
+Palladium

contrib/daemontools/env/DAEMON_URL

@@ -1 +1 @@
-http://username:password@host:port/
+http://username:password@127.0.0.1:2332/

contrib/daemontools/env/DB_ENGINE

@@ -0,0 +1 @@
+rocksdb

contrib/daemontools/env/SERVICES

@@ -0,0 +1 @@
+tcp://:50001,rpc://