docs: rebrand documentation, packaging, and helper scripts to DragonX

The docs/packaging were largely un-rebranded Hush3 content, with several
docs stating facts that are wrong for DragonX. This rewrites them against
the verified DragonX source state.

Corrections (not just branding):
- PoW: RandomX (CPU), not Equihash/ASIC — README, overview.md, randomx.md
- Privacy: private from genesis (ac_private=1, Sapling@height1), not "as of
  block 340000" — overview.md, payment-api.md
- Removed the false "coinbase must be shielded" consensus claim
  (shield-coinbase.md, payment-api.md); coinbase is directly spendable
- Fixed default fee 0.0001 (was 0.0010000, 10x); stratum port 22769 (was 19031)
- datadir ~/.hush/DRAGONX, DRAGONX.conf, dragonxd/dragonx-cli/dragonx-tx,
  git.dragonx.is throughout; branch model dev->dragonx
- Softened the inherited dPoW reorg claim (no live DragonX notary infra)

Packaging: fix build-debian-package.sh + gen-manpages.sh to use the dragonx
binaries/manpages; rename bash-completions to dragonx*; drop hush-arrakis-chain
from the package. Keep /usr/share/hush (hardcoded in the binary for params).

Also: README links/logo, ObsidianDragon + SilentDragonXAndroid wallets,
networking/init/dev-process/contrib/util rebrand, and leftover helper scripts.
Delete legacy duplicates (hushd.* init/service, HUSH3.conf examples,
OLD_WALLETS.md, hsc.md) and rename hush-uri.bat -> dragonx-uri.bat.

Out of scope (noted, not changed): historical changelog/copyright, the Hush
mainnet airdrop snapshot, seed data files, depends/ source mirrors, and the
in-code strCurrencyUnits="HUSH".

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

contrib/convert_address.py

@@ -11,7 +11,7 @@ from hashlib import sha256
 # based on https://github.com/KMDLabs/pos64staker/blob/master/stakerlib.py#L89
 def addr_convert(prefix, address, prefix_bytes):
     rmd160_dict  = {}
-    # ZEC/HUSH/etc have 2 prefix bytes, BTC/KMD only have 1
+    # ZEC/DRAGONX/etc have 2 prefix bytes, BTC/KMD only have 1
     # NOTE: any changes to this code should be verified against https://dexstats.info/addressconverter.php
     ripemd       = b58decode_check(address).hex()[2*prefix_bytes:]
     net_byte     = prefix + ripemd
@@ -23,7 +23,7 @@ def addr_convert(prefix, address, prefix_bytes):
     return(final.decode())
 
 if len(sys.argv) < 2:
-    sys.exit('Usage: %s hushv2address' % sys.argv[0])
+    sys.exit('Usage: %s dragonxv2address' % sys.argv[0])
 
 address = sys.argv[1]
 # convert given address to a KMD address