Add configurable LNbits invoice memos and pubkey metadata

Read INVOICE_MEMO_YEARLY and INVOICE_MEMO_LIFETIME from the environment
and pass the user pubkey in LNbits payment extra for invoice creation.

.env.example

@@ -20,6 +20,8 @@ LNBITS_INVOICE_KEY=your-lnbits-invoice-read-key
 PRICE_YEARLY_SATS=1000
 PRICE_LIFETIME_SATS=10000
 INVOICE_EXPIRY_MINUTES=30
+INVOICE_MEMO_YEARLY=Noderunners Relay yearly Access
+INVOICE_MEMO_LIFETIME=Noderunners Relay lifetime Access
 
 # --- Nostr ---
 RELAYS=wss://relay.azzamo.net,wss://nostr.azzamo.net,wss://wot.azzamo.net