chainparams: do not let other smart chains inherit DragonX's seeds

A smart chain builds its params by copying a base network and
overriding pieces, but nothing ever touched vSeeds/vFixedSeeds. That is
how DRAGONX ran on Hush's seeds -- seed1.hush.is and friends, long
since gone from DNS -- for as long as it did, and it means any other
assetchain started from this binary now inherits DragonX's.

Seeds are per-chain by nature: an address serving one chain is useless
to another, and dialling it is at best wasted effort and at worst a
peer speaking a different protocol. DRAGONX keeps the seeds configured
in CMainParams, which are its own; every other chain starts empty and
relies on -addnode/-connect, which an assetchain operator has to
configure regardless.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FU87LdsJZiZkfq1eXubpeo

src/chainparams.h

@@ -117,6 +117,10 @@ public:
     void SetNValue(uint64_t n) { nEquihashN = n; }
     void SetKValue(uint64_t k) { nEquihashK = k; }
     void SetMiningRequiresPeers(bool flag) { fMiningRequiresPeers = flag; }
+    //! Drop any inherited peer seeds. An assetchain gets its params by copying a
+    //! base network and overriding pieces; without this it silently keeps the base
+    //! chain's DNS and fixed seeds, which are wrong for it by definition.
+    void ClearSeeds() { vSeeds.clear(); vFixedSeeds.clear(); }
 
     CMessageHeader::MessageStartChars pchMessageStart;
     Consensus::Params consensus;