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>

qa/rpc-tests/README.md

@@ -20,7 +20,7 @@ Possible options:
 -h, --help       show this help message and exit
   --nocleanup      Leave binaries and test.* datadir on exit or error
   --noshutdown     Don't stop full node after the test execution
-  --srcdir=SRCDIR  Source directory containing hushd/hush-cli (default: ../../src)
+  --srcdir=SRCDIR  Source directory containing dragonxd/dragonx-cli (default: ../../src)
   --tmpdir=TMPDIR  Root directory for datadirs
   --tracerpc       Print out all RPC calls as they are made
 ```
@@ -30,7 +30,9 @@ If you set the environment variable `PYTHON_DEBUG=1` you will get some debug out
 A 200-block -regtest blockchain and wallets for four nodes
 is created the first time a regression test is run and
 is stored in the cache/ directory.  Each node has the miner
-subsidy from 25 mature blocks (`25*10=250 HUSH`) in its wallet.
+subsidy from 25 mature blocks in its wallet. The exact amount in DRAGONX
+depends on the per-test `-ac_reward` (regtest subsidy), so it is not a
+fixed figure across tests.
 
 After the first run, the cache/ blockchain and wallets are
 copied into a temporary directory and used as the initial
@@ -40,7 +42,7 @@ If you get into a bad state, you should be able to recover with:
 
 ```bash
 rm -rf cache
-killall hushd
+killall dragonxd
 ```
 
 but beware that could kill various other processes you might not want to kill!