Cdk ldk node (#904)

* feat: add LDK Node Lightning backend with comprehensive integration

- Add new cdk-ldk-node crate implementing Lightning backend using LDK Node
- Extend MintPayment trait with start/stop methods for processor lifecycle management
- Add LDK Node configuration support to cdk-mintd with chain source and gossip options
- Enhance mint startup/shutdown to properly manage payment processor lifecycle

---------

Co-authored-by: Erik <78821053+swedishfrenchpress@users.noreply.github.com>

crates/cdk-sql-common/src/mint/mod.rs

@@ -546,6 +546,11 @@ where
         amount_paid: Amount,
         payment_id: String,
     ) -> Result<Amount, Self::Err> {
+        if amount_paid == Amount::ZERO {
+            tracing::warn!("Amount payments of zero amount should not be recorded.");
+            return Err(Error::Duplicate);
+        }
+
         // Check if payment_id already exists in mint_quote_payments
         let exists = query(
             r#"
@@ -592,6 +597,13 @@ where
             .checked_add(amount_paid)
             .ok_or_else(|| database::Error::AmountOverflow)?;
 
+        tracing::debug!(
+            "Mint quote {} amount paid was {} is now {}.",
+            quote_id,
+            current_amount_paid,
+            new_amount_paid
+        );
+
         // Update the amount_paid
         query(
             r#"