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/block_time.pl

@@ -8,17 +8,17 @@ use strict;
 # Given a block height, estimate when it will happen
 my $block      = shift || die "Usage: $0 123";
 my $coin       = shift || '';
-my $hush       = "./src/hush-cli";
-unless (-e $hush) {
-    die "$hush does not exist, aborting";
+my $cli        = "./src/dragonx-cli";
+unless (-e $cli) {
+    die "$cli does not exist, aborting";
 }
 if ($coin) {
-    $hush .= " -ac_name=$coin";
+    $cli .= " -ac_name=$coin";
 }
-my $blockcount = qx{$hush getblockcount};
+my $blockcount = qx{$cli getblockcount};
 
 unless ($blockcount = int($blockcount)) {
-    print "Invalid response from $hush\n";
+    print "Invalid response from $cli\n";
     exit 1;
 }
 
@@ -28,7 +28,7 @@ if ($block <= $blockcount) {
 	my $diff    = $block - $blockcount;
     # TODO: support custom blocktimes
     # assumes HACs use default blocktime of 60s
-    my $minpb   = $coin ? 1 : 1.25; # 75s in minutes for HUSH3
+    my $minpb   = $coin ? 1 : 0.6; # 36s in minutes for DragonX
 	my $minutes = $diff*$minpb;
 	my $seconds = $minutes*60;
 	my $now     = time;
@@ -38,7 +38,7 @@ if ($block <= $blockcount) {
     if ($coin) {
 	    print "$coin Block $block will happen at roughly:\n";
     } else {
-	    print "Hush Block $block will happen at roughly:\n";
+	    print "DragonX Block $block will happen at roughly:\n";
     }
 	print "$ldate Eastern # $then\n";
 	print "$gmdate GMT     # $then\n";