Fork xmrcheckout for Wownero (WOW)

Minimal changes from upstream xmrcheckout to support Wownero:
- Rate provider: Nonlogs WOW-BTC via Kraken BTC/USD
- Subaddress derivation: Wownero network byte overrides (53/63/54)
- Payment URI scheme: wownero:
- Dockerfile: Wownero binaries from Codeberg
- Display text: Monero→Wownero, XMR→WOW throughout UI
- Default daemon: 192.168.88.235:34568
- Added wownero-logo.svg

File and folder structure kept identical to upstream for easy sync.

api/app/subaddress_derivation.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from binascii import hexlify, unhexlify
+import struct
+
+from monero import base58, const, ed25519
+from monero.address import Address
+from monero.keccak import keccak_256
+
+# Override monero library network constants for Wownero
+from monero import const as _mc
+_mc.NETS = ('main',)
+_mc.MASTERADDR_NETBYTES = (53,)   # Wownero mainnet address prefix
+_mc.SUBADDR_NETBYTES = (63,)      # Wownero subaddress prefix
+_mc.INTADDRR_NETBYTES = (54,)     # Wownero integrated address prefix
+
+
+def derive_subaddress(
+    *,
+    payment_address: str,
+    view_key: str,
+    account_index: int,
+    address_index: int,
+) -> str:
+    address = Address(payment_address)
+    view_key_bytes = unhexlify(view_key)
+    spend_pub_bytes = unhexlify(address.spend_key())
+
+    data = (
+        b"SubAddr\0"
+        + view_key_bytes
+        + struct.pack("<II", account_index, address_index)
+    )
+    m = ed25519.scalar_reduce(keccak_256(data).digest())
+    mG = ed25519.scalarmult_B(m)
+    D = ed25519.edwards_add(spend_pub_bytes, mG)
+    C = ed25519.scalarmult(view_key_bytes, D)
+    prefix = const.SUBADDR_NETBYTES[const.NETS.index(address.net)]
+    payload = bytearray([prefix]) + D + C
+    checksum = keccak_256(payload).digest()[:4]
+    return base58.encode(hexlify(payload + checksum))