cleanup: rebrand residual user-facing "HUSH" strings to DragonX

Sweeps the leftover coin-name strings in RPC help text, RPC output, and log
messages that the currency-unit change didn't cover:

- RPC help: "mining reward amount in HUSH" -> DRAGONX (mining.cpp x2);
  "at least minbal HUSH" -> DRAGONX (rpcwallet.cpp); "the HUSH address" /
  "(string) HUSH address" -> DragonX (rawtransaction.cpp)
- RPC output: the SMART_CHAIN_SYMBOL[0]==0 ? "HUSH" : SYMBOL coin-name fallback
  (crosschain/misc/mining/blockchain) -> "DRAGONX"; the notarizations JSON key
  make_pair("HUSH", ...) -> "DRAGONX"
- Logs: "HUSH blocktime changing", "stopping HUSH HTTP/REST/RPC",
  "HUSH raw magic=" -> DragonX

Left untouched (verified): the 82 "HUSH3"/ishush3 chain-symbol consensus checks;
hush_globals.h CURRENCIES[] price-oracle basket (internal lookup, dead feature
on DragonX); hush.h notarization debug printf; a commented-out cout in main.cpp.

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

src/rpc/rawtransaction.cpp

@@ -628,7 +628,7 @@ UniValue createrawtransaction(const UniValue& params, bool fHelp, const CPubKey&
             "     ]\n"
             "2. \"outputs\"               (object, required) a json object with outputs\n"
             "    {\n"
-            "      \"address\": x.xxx,    (numeric or string, required) The key is the HUSH address or script (in hex), the numeric value (can be string) is the " + CURRENCY_UNIT + " amount\n"
+            "      \"address\": x.xxx,    (numeric or string, required) The key is the DragonX address or script (in hex), the numeric value (can be string) is the " + CURRENCY_UNIT + " amount\n"
             "      \"data\": \"hex\"      (string, optional) The key is \"data\", the value is hex encoded OP_RETURN data\n"
             "      ,...\n"
             "    }\n"
@@ -804,7 +804,7 @@ UniValue decoderawtransaction(const UniValue& params, bool fHelp, const CPubKey&
             "         \"reqSigs\" : n,            (numeric) The required sigs\n"
             "         \"type\" : \"pubkeyhash\",  (string) The type, eg 'pubkeyhash'\n"
             "         \"addresses\" : [           (json array of string)\n"
-            "           \"RTZMZHDFSTFQst8XmX2dR4DaH87cEUs3gC\"   (string) HUSH address\n"
+            "           \"RTZMZHDFSTFQst8XmX2dR4DaH87cEUs3gC\"   (string) DragonX address\n"
             "           ,...\n"
             "         ]\n"
             "       }\n"