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>

lnbits/static/js/pages/wallet.js

@@ -308,16 +308,17 @@ window.PageWallet = {
       }
 
       // Check if invoice is amountless (no amount specified)
+      // The decoder returns 'Any amount' string for amountless invoices
+      const invoiceAmount = invoice.human_readable_part.amount
       const isAmountless =
-        !invoice.human_readable_part.amount ||
+        typeof invoiceAmount !== 'number' || invoiceAmount <= 0
-        invoice.human_readable_part.amount === 0
 
       let cleanInvoice = {
-        msat: isAmountless ? null : invoice.human_readable_part.amount,
+        msat: isAmountless ? null : invoiceAmount,
-        sat: isAmountless ? null : invoice.human_readable_part.amount / 1000,
+        sat: isAmountless ? null : invoiceAmount / 1000,
         fsat: isAmountless
           ? this.$t('any_amount')
-          : LNbits.utils.formatSat(invoice.human_readable_part.amount / 1000),
+          : LNbits.utils.formatSat(invoiceAmount / 1000),
         bolt11: this.parse.data.request,
         isAmountless: isAmountless
       }