feat: add negative topups (#2835)

* feat: add negative topups
* remove topup dialog

---------

Co-authored-by: Vlad Stan <stan.v.vlad@gmail.com>

lnbits/wallets/fake.py

@@ -1,6 +1,6 @@
 import asyncio
-import hashlib
 from datetime import datetime
+from hashlib import sha256
 from os import urandom
 from typing import AsyncGenerator, Dict, Optional, Set
 
@@ -16,6 +16,7 @@ from bolt11 import (
 from loguru import logger
 
 from lnbits.settings import settings
+from lnbits.utils.crypto import fake_privkey
 
 from .base import (
     InvoiceResponse,
@@ -35,14 +36,8 @@ class FakeWallet(Wallet):
         self.queue: asyncio.Queue = asyncio.Queue(0)
         self.payment_secrets: Dict[str, str] = {}
         self.paid_invoices: Set[str] = set()
-        self.secret: str = settings.fake_wallet_secret
-        self.privkey: str = hashlib.pbkdf2_hmac(
-            "sha256",
-            self.secret.encode(),
-            b"FakeWallet",
-            2048,
-            32,
-        ).hex()
+        self.secret = settings.fake_wallet_secret
+        self.privkey = fake_privkey(self.secret)
 
     async def cleanup(self):
         pass
@@ -71,7 +66,7 @@ class FakeWallet(Wallet):
         elif unhashed_description:
             tags.add(
                 TagChar.description_hash,
-                hashlib.sha256(unhashed_description).hexdigest(),
+                sha256(unhashed_description).hexdigest(),
             )
         else:
             tags.add(TagChar.description, memo or "")
@@ -85,7 +80,7 @@ class FakeWallet(Wallet):
             secret = urandom(32).hex()
         tags.add(TagChar.payment_secret, secret)
 
-        payment_hash = hashlib.sha256(secret.encode()).hexdigest()
+        payment_hash = sha256(secret.encode()).hexdigest()
 
         tags.add(TagChar.payment_hash, payment_hash)