feat: implement automatic crediting of new accounts with 1 million satoshis

- Modified the user account creation process to automatically credit new
accounts with 1,000,000 satoshis upon creation.
- Updated the `create_user_account_no_ckeck` function to include error
handling and logging for the credit operation.
- Enhanced tests to verify the balance for newly registered users,
ensuring the correct credit amount is applied.
- Documented affected account creation paths and testing instructions in
the new `AUTO_CREDIT_CHANGES.md` file.

fix: pass db connection to update_wallet_balance to prevent SQLite deadlock

The auto-credit feature was causing a deadlock on SQLite because
update_wallet_balance was opening a new database connection while
already inside a transaction. By passing conn=conn, we reuse the
existing connection and avoid the deadlock.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

AUTO_CREDIT_CHANGES.md

@@ -0,0 +1,88 @@
+# LNBits Auto-Credit Changes
+
+## Overview
+Modified LNBits server to automatically credit new accounts with 1 million satoshis (1,000,000 sats) when they are created.
+
+## Changes Made
+
+### 1. Modified `lnbits/core/services/users.py`
+
+**Added imports:**
+- `get_wallet` from `..crud`
+- `update_wallet_balance` from `.payments`
+
+**Modified `create_user_account_no_ckeck` function:**
+- Changed `create_wallet` call to capture the returned wallet object
+- Added automatic credit of 1,000,000 sats after wallet creation
+- Added error handling and logging for the credit operation
+
+**Code changes:**
+```python
+# Before:
+await create_wallet(
+    user_id=account.id,
+    wallet_name=wallet_name or settings.lnbits_default_wallet_name,
+)
+
+# After:
+wallet = await create_wallet(
+    user_id=account.id,
+    wallet_name=wallet_name or settings.lnbits_default_wallet_name,
+)
+
+# Credit new account with 1 million satoshis
+try:
+    await update_wallet_balance(wallet, 1_000_000)
+    logger.info(f"Credited new account {account.id} with 1,000,000 sats")
+except Exception as e:
+    logger.error(f"Failed to credit new account {account.id} with 1,000,000 sats: {e}")
+```
+
+### 2. Updated Tests in `tests/api/test_auth.py`
+
+**Modified test functions:**
+- `test_register_ok`: Added balance verification for regular user registration
+- `test_register_nostr_ok`: Added balance verification for Nostr authentication
+
+**Added assertions:**
+```python
+# Check that the wallet has 1 million satoshis
+wallet = user.wallets[0]
+assert wallet.balance == 1_000_000, f"Expected 1,000,000 sats balance, got {wallet.balance} sats"
+```
+
+## Affected Account Creation Paths
+
+The automatic credit will be applied to all new accounts created through:
+
+1. **Regular user registration** (`/api/v1/auth/register`)
+2. **Nostr authentication** (`/api/v1/auth/nostr`)
+3. **SSO login** (when new account is created)
+4. **API account creation** (`/api/v1/account`)
+5. **Admin user creation** (via admin interface)
+
+## Excluded Paths
+
+- **Superuser/Admin account creation** (`init_admin_settings`): This function creates the admin account directly and bypasses the user creation flow, so it won't receive the automatic credit.
+
+## Testing
+
+To test the changes:
+
+1. Install dependencies: `poetry install`
+2. Run the modified tests: `poetry run pytest tests/api/test_auth.py::test_register_ok -v`
+3. Run Nostr test: `poetry run pytest tests/api/test_auth.py::test_register_nostr_ok -v`
+
+## Logging
+
+The system will log:
+- Success: `"Credited new account {account.id} with 1,000,000 sats"`
+- Failure: `"Failed to credit new account {account.id} with 1,000,000 sats: {error}"`
+
+## Notes
+
+- The credit uses the existing `update_wallet_balance` function which creates an internal payment record
+- The credit is applied after wallet creation but before user extensions are set up
+- Error handling ensures that account creation continues even if the credit fails
+- The credit amount is hardcoded to 1,000,000 sats (1MM sats)
+