Compliant rebrand: legal compliance, code audit, and documentation (Phases 0-3)

Phase 0 - Legal Compliance:
- COPYING: Add DragonX copyright, preserve all upstream attributions
- AUTHORS: Add DragonX developers section
- LICENSE: Restore standard FSF GPLv3 text (fix GNU→GENERAL error)
- Add DragonX copyright headers to all 21 modified source files
- contrib/debian/copyright: Add DragonX attribution
- README.md: Add GPLv3 Section 5(a) attribution section

Phase 1 - init.cpp Cleanup:
- PID file: hushd.pid → dragonxd.pid
- Shutdown thread: hush-shutoff → dragonx-shutoff
- Debug message: stopping HUSH → stopping DragonX

Phase 2 - HUSH3/ishush3 Code Audit:
- Rename ishush3 → isdragonx across ~15 source files
- Update "HUSH3" chain-identity checks to "DRAGONX" in consensus,
  difficulty, notarization, devtax, and RPC code
- Intentionally preserve cross-chain "HUSH3" refs (gateway, notary dest)
- Build verified: all three binaries compile cleanly

Phase 3 - Documentation:
- README.md: Full rewrite with DragonX chain params, build instructions
- Man pages: Create dragonxd.1, dragonx-cli.1, dragonx-tx.1 (v1.0.0)
- Doc files: Add beefy-DRAGONX.conf, dragonxd-systemd.md, dragonxd.service
- Init scripts: Create dragonxd.{conf,init,openrc,openrcconf,service}
- Debian packaging: Update control, changelog, install, manpages, examples
- Update doc/init.md and contrib/init/README.md

contrib/init/dragonxd.init

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+#
+#  dragonxd The hush core server.
+#
+#
+# chkconfig: 345 80 20
+# description: dragonxd
+# processname: dragonxd
+#
+
+# Source function library.
+. /etc/init.d/functions
+
+# you can override defaults in /etc/sysconfig/dragonxd, see below
+if [ -f /etc/sysconfig/dragonxd ]; then
+        . /etc/sysconfig/dragonxd
+fi
+
+RETVAL=0
+
+prog=dragonxd
+# you can override the lockfile via HUSHD_LOCKFILE in /etc/sysconfig/dragonxd
+lockfile=${HUSHD_LOCKFILE-/var/lock/subsys/dragonxd}
+
+# dragonxd defaults to /usr/bin/dragonxd, override with HUSHD_BIN
+dragonxd=${HUSHD_BIN-/usr/bin/dragonxd}
+
+# dragonxd opts default to -disablewallet, override with HUSHD_OPTS
+dragonxd_opts=${HUSHD_OPTS--disablewallet}
+
+start() {
+    echo -n $"Starting $prog: "
+    daemon $DAEMONOPTS $dragonxd $dragonxd_opts
+    RETVAL=$?
+    echo
+    [ $RETVAL -eq 0 ] && touch $lockfile
+    return $RETVAL
+}
+
+stop() {
+    echo -n $"Stopping $prog: "
+    killproc $prog
+    RETVAL=$?
+    echo
+    [ $RETVAL -eq 0 ] && rm -f $lockfile
+    return $RETVAL
+}
+
+case "$1" in
+    start)
+        start
+        ;;
+    stop)
+        stop
+        ;;
+    status)
+        status $prog
+        ;;
+    restart)
+        stop
+        start
+        ;;
+    *)
+        echo "Usage: service $prog {start|stop|status|restart}"
+        exit 1
+        ;;
+esac