cleanup: rebrand currency unit, depends mirrors, seeds; drop Hush-history files

Follow-up to the doc rebrand, addressing the previously out-of-scope legacy:

- Currency unit: strCurrencyUnits (chainparams.cpp) and CURRENCY_UNIT
  (amount.cpp) "HUSH" -> "DRAGONX". Both are display-only (RPC help + metrics);
  no logic comparisons, verified.
- depends mirrors: libsodium/boost/utfcpp fetched from git.hush.is/attachments;
  repointed to canonical upstream (GitHub release / archives.boost.io / GitHub
  tag) with the existing sha256 hashes verified to match those sources.
- Seeds: nodes_main.txt now lists the five node[1-5].dragonx.is IPs (DNS-resolved)
  instead of Hush nodes; regenerated src/chainparamsseeds.h (was compiling Hush
  seed IPs as the fixed fallback); generate-seeds.py header now says DragonX;
  hush_seed_nodes.txt updated to DragonX seeds.
- Deleted Hush-history / wrong-for-DragonX files: contrib/snapshot/ (block-500000
  Hush airdrop, ~10MB), notary_seeds.txt (Hush notaries; DragonX isn't notarized),
  and the Hush emission scripts hush_supply, hush_supply_old, hush_halvings,
  hush_block_subsidy_per_halving (hardcode Hush's 340000/12.5 economics).

Kept: hush_scanner (engine invoked by dragonx_scanner) and the "The Hush
developers" copyright headers (lineage credit).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/chainparamsseeds.h

@@ -5,29 +5,17 @@
 // Instead, update contrib/seeds/nodes_main.txt then run
 //    ./contrib/seeds/generate-seeds.py contrib/seeds > src/chainparamsseeds.h
 // OR run: make seeds
-#ifndef HUSH_CHAINPARAMSSEEDS_H
-#define HUSH_CHAINPARAMSSEEDS_H
-// List of fixed seed nodes for the Hush network
+#ifndef DRAGONX_CHAINPARAMSSEEDS_H
+#define DRAGONX_CHAINPARAMSSEEDS_H
+// List of fixed seed nodes for the DragonX network
 // Each line contains a BIP155 serialized address.
 //
 static const uint8_t chainparams_seed_main[] = {
-    0x01,0x04,0x67,0x45,0x80,0x94,0x00,0x00, // 103.69.128.148
-    0x01,0x04,0xc2,0x1d,0x64,0xb3,0x00,0x00, // 194.29.100.179
-    0x01,0x04,0x2d,0x84,0x4b,0x45,0x00,0x00, // 45.132.75.69
-    0x01,0x04,0xaa,0xcd,0x27,0x27,0x00,0x00, // 170.205.39.39
-    0x01,0x04,0x95,0x1c,0x66,0xdb,0x00,0x00, // 149.28.102.219
-    0x01,0x04,0x9b,0x8a,0xe4,0x44,0x00,0x00, // 155.138.228.68
-    0x01,0x04,0x6b,0xae,0x46,0xfb,0x00,0x00, // 107.174.70.251
-    0x01,0x04,0xb2,0xfa,0xbd,0x8d,0x00,0x00, // 178.250.189.141
-    0x04,0x20,0x0e,0x86,0xb6,0xfd,0x96,0xfe,0x06,0xda,0x39,0xeb,0x97,0x39,0xc9,0xd1,0x17,0xa2,0x4e,0x2b,0x75,0x4d,0xeb,0xb5,0xa1,0x34,0x1e,0x34,0x0a,0xcb,0x68,0xab,0xf0,0xe2,0x00,0x00, // b2dln7mw7ydnuopls444tuixujhcw5kn5o22cna6gqfmw2fl6drb5nad.onion
-    0x04,0x20,0x1c,0x96,0x10,0x03,0xa6,0xa4,0xfa,0xa0,0x3e,0x13,0x1f,0x38,0xf0,0x9b,0xdd,0x9b,0xd7,0xdc,0x0e,0x40,0x61,0x71,0xed,0x1d,0x21,0x58,0xce,0x59,0x55,0x5e,0xe4,0x25,0x00,0x00, // dslbaa5gut5kapqtd44pbg65tpl5ydsamfy62hjbldhfsvk64qs57pyd.onion
-    0x04,0x20,0xac,0xa0,0x3a,0x31,0xa7,0xea,0x8e,0x90,0xc7,0x2b,0xbb,0x89,0x41,0x05,0x48,0xa0,0x10,0x29,0x8f,0x38,0x16,0xc9,0x94,0xbe,0xef,0x7e,0x9e,0x7d,0x98,0xb6,0x76,0x9f,0x00,0x00, // vsqdumnh5khjbrzlxoeucbkiuaictdzyc3ezjpxpp2ph3gfwo2ptjmyd.onion
-    0x02,0x10,0x2a,0x0c,0xb6,0x41,0x06,0xf1,0x01,0x8e,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x02,0x00,0x00, // 2a0c:b641:6f1:18e::2
-    0x02,0x10,0x24,0x06,0xef,0x80,0x00,0x03,0x12,0x69,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x00,0x00, // 2406:ef80:3:1269::1
-    0x02,0x10,0x24,0x06,0xef,0x80,0x00,0x02,0x3b,0x59,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x00,0x00, // 2406:ef80:2:3b59::1
-    0x02,0x10,0x24,0x06,0xef,0x80,0x00,0x01,0x14,0x6e,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x00,0x00, // 2406:ef80:1:146e::1
-    0x02,0x10,0x24,0x06,0xef,0x80,0x00,0x04,0x21,0x32,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0x00,0x00, // 2406:ef80:4:2132::1
-    0x05,0x20,0xfb,0xa8,0xca,0x3d,0xf4,0xc9,0x83,0x95,0xa8,0x07,0x05,0x6f,0xf8,0x46,0x69,0x6d,0x42,0x75,0x22,0xe9,0x80,0xd8,0x43,0x7c,0xbe,0x29,0xda,0x33,0x14,0xf9,0xfb,0x17,0x00,0x00, // 7oumuppuzgbzlkahavx7qrtjnvbhkixjqdmeg7f6fhndgfhz7mlq.b32.i2p
+    0x01,0x04,0xd4,0x38,0x29,0x3f,0x00,0x00, // 212.56.41.63
+    0x01,0x04,0xc2,0x8c,0xc6,0xb0,0x00,0x00, // 194.140.198.176
+    0x01,0x04,0xd4,0x38,0x29,0x2f,0x00,0x00, // 212.56.41.47
+    0x01,0x04,0x90,0x7e,0x93,0xa5,0x00,0x00, // 144.126.147.165
+    0x01,0x04,0xb0,0x7e,0x57,0xf1,0x00,0x00, // 176.126.87.241
 };
 
 static const uint8_t chainparams_seed_test[] = {