Rebrand hush3 to DragonX and share RandomX dataset across mining threads

Minimal rebrand (see compliant-rebrand branch for full rebrand):
- Rename binaries: hushd/hush-cli/hush-tx → dragonxd/dragonx-cli/dragonx-tx
- Default to DRAGONX chain params without -ac_* flags (randomx, blocktime=36, private=1)
- Update configure.ac: AC_INIT([DragonX],[1.0.0])
- Update client version string and user-agent to /DragonX:1.0.0/
- Add chainparams.cpp with DRAGONX network parameters
- Update build.sh, miner.cpp, pow.cpp for DragonX
- Add bootstrap-dragonx.sh utility script
- Update .gitignore for release directory

Share single RandomX dataset across all mining threads:
- Add RandomXDatasetManager with readers-writer lock, reducing RAM from
  ~2GB per thread to ~2GB total plus ~2MB per thread for the VM scratchpad
- Add LogProcessMemory() diagnostic helper for Linux and Windows

src/version.h

@@ -21,7 +21,8 @@
 #define HUSH_VERSION_H
 
 // network protocol versioning
-static const int PROTOCOL_VERSION = 1987429;
+// DragonX 1.0.0 - bumped to separate from old HUSH/DragonX nodes with RandomX bug
+static const int PROTOCOL_VERSION = 2000000;
 //! initial proto version, to be increased after version/verack negotiation
 static const int INIT_PROTO_VERSION = 209;
 //! In this version, 'getheaders' was introduced.
@@ -30,8 +31,9 @@ static const int GETHEADERS_VERSION = 31800;
 //! disconnect from peers older than this proto version (HUSH mainnet)
 static const int MIN_HUSH_PEER_PROTO_VERSION = 1987426;
 
-//! disconnect from peers older than this proto version (HACs)
-static const int MIN_PEER_PROTO_VERSION = 1987420;
+//! disconnect from peers older than this proto version (DragonX/HACs)
+//! Set to 2000000 to reject nodes without RandomX validation fix
+static const int MIN_PEER_PROTO_VERSION = 2000000;
 
 //! nTime field added to CAddress, starting with this version;
 //! if possible, avoid requesting addresses nodes older than this