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>

ISSUE_TEMPLATE.md

@@ -1,8 +1,8 @@
 <!--- Remove text and sections that do not apply -->
 
-This issue tracker is only for technical issues related to hushd
+This issue tracker is only for technical issues related to dragonxd
 
-General Hush questions and/or support requests and are best directed to [Telegram](https://hush.is/telegram_support)
+General DragonX questions and/or support requests are best directed to [Telegram](https://dragonx.is/tg) or [Matrix](https://dragonx.is/matrix).
 
 ### Describe the issue
 
@@ -23,9 +23,9 @@ Tell us what should happen
 
 Tell us what happens instead including any noticable error output (any messages displayed on-screen when e.g. a crash occurred)
 
-### The version of Hush you were using:
+### The version of DragonX you were using:
 
-Run `hushd --version` to find out
+Run `dragonxd --version` to find out
 
 ### Machine specs:
 - OS name + version:
@@ -38,7 +38,7 @@ Run `hushd --version` to find out
 
 ### Any extra information that might be useful in the debugging process.
 
-This includes the relevant contents of `~/.hush/HUSH3/debug.log` or `~/.komodo/HUSH3/debug.log` if you have a legacy install. You can paste raw text, attach the file directly in the issue or link to the text via a pastebin type site.
+This includes the relevant contents of `~/.hush/DRAGONX/debug.log`. You can paste raw text, attach the file directly in the issue or link to the text via a pastebin type site.
 Please also include any non-standard things you did during compilation (extra flags, dependency version changes etc.) if applicable.
 
 Beware that usernames and IP addresses and other metadata is definitely in this log file!