hygiene: Phase 4 — route unconditional debug output through LogPrint

Fourth phase of the code-hygiene remediation, addressing the ~1,082 stray
fprintf(stderr)/printf debug calls so consensus and hot paths stop spewing
to stderr/stdout. Done per-file (18 files) with conservative rules; the tree
builds clean, self-mines, and `verifychain` re-validates the whole chain
(pow/txdb/coins/miner paths) with -debug=1 enabling every converted line —
zero tinyformat/format-arg exceptions.

Net across 18 files: 174 commented-out debug lines deleted, 173 unconditional
live prints converted to LogPrint("<cat>",...)/LogPrintf (net/mining/pow/nspv/
zrpc categories, format strings + args preserved exactly), 40 pure-noise or
sensitive prints deleted, and 194 calls DELIBERATELY LEFT (already behind
fDebug/fZdebug guards, or genuine startup/fatal-error output that must reach
the console before logging init).

Notable:
- Deleted sensitive success-path dumps (nSPV SIG_TXHASH + full tx input/
  output/change amounts; kvupdate privkey/pubkey hex) that were writing key
  and amount material straight to stderr/stdout.
- Removed the raw 32-byte target hex dumps in the zawy adaptive-PoW helpers
  and the legacy one-shot `if(height==340000)` HUSH artifact in pow.cpp.
- Converted per-tx relay + ban/banlist (net), per-setgenerate MININGTHREADS
  (rpc/mining), signrawtransaction TXPOW, and per-message nSPV traces.
- Left format/arg-mismatched lines untouched (flagged) to avoid introducing
  tinyformat runtime throws.

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

src/wallet/rpcdump.cpp

@@ -1231,7 +1231,6 @@ UniValue nspv_listtransactions(const UniValue& params, bool fHelp, const CPubKey
             CCflag = atoi((char *)params[1].get_str().c_str());
         if ( params.size() == 3 )
             skipcount = atoi((char *)params[2].get_str().c_str());
-        //fprintf(stderr,"call txids cc.%d skip.%d\n",CCflag,skipcount);
         return(NSPV_addresstxids((char *)params[0].get_str().c_str(),CCflag,skipcount,0));
     }
     else throw runtime_error("nspv_listtransactions [address [isCC [skipcount]]]\n");
@@ -1294,7 +1293,6 @@ UniValue nspv_spend(const UniValue& params, bool fHelp, const CPubKey& mypk)
     if ( NSPV_address.size() == 0 )
         throw runtime_error("to nspv_send you need an active nspv_login\n");
     satoshis = atof(params[1].get_str().c_str())*COIN + 0.0000000049;
-    //fprintf(stderr,"satoshis.%lld from %.8f\n",(long long)satoshis,atof(params[1].get_str().c_str()));
     if ( satoshis < 1000 )
         throw runtime_error("amount too small\n");
     return(NSPV_spend((char *)NSPV_address.c_str(),(char *)params[0].get_str().c_str(),satoshis));