Migrate EntropyError and BuildError to UniFFI proc-macro export

Add `#[derive(uniffi::Error)]` to `EntropyError` and `BuildError`,
replacing their UDL definitions with `typedef enum` references.

Generated with the help of AI (Claude Code).

Co-Authored-By: HAL 9000

Author: tnull

bindings/ldk_node.udl

@@ -66,10 +66,7 @@ interface NodeEntropy {
 	constructor(string seed_path);
 };
 
-enum EntropyError {
-	"InvalidSeedBytes",
-	"InvalidSeedFile",
-};
+typedef enum EntropyError;
 
 typedef enum WordCount;
 
@@ -379,23 +376,7 @@ dictionary BestBlock {
 	u32 height;
 };
 
-[Error]
-enum BuildError {
-	"InvalidSystemTime",
-	"InvalidChannelMonitor",
-	"InvalidListeningAddresses",
-	"InvalidAnnouncementAddresses",
-	"InvalidNodeAlias",
-	"RuntimeSetupFailed",
-	"ReadFailed",
-	"WriteFailed",
-	"StoragePathAccessFailed",
-	"KVStoreSetupFailed",
-	"WalletSetupFailed",
-	"LoggerSetupFailed",
-	"NetworkMismatch",
-	"AsyncPaymentsConfigMismatch",
-};
+typedef enum BuildError;
 
 [Trait, WithForeign]
 interface VssHeaderProvider {

src/builder.rs

@@ -154,6 +154,7 @@ impl std::fmt::Debug for LogWriterConfig {
 ///
 /// [`Node`]: crate::Node
 #[derive(Debug, Clone, PartialEq)]
+#[cfg_attr(feature = "uniffi", derive(uniffi::Error))]
 pub enum BuildError {
 	/// The current system time is invalid, clocks might have gone backwards.
 	InvalidSystemTime,

src/entropy.rs

@@ -16,6 +16,7 @@ use crate::io;
 
 /// An error that could arise during [`NodeEntropy`] construction.
 #[derive(Debug, Clone, PartialEq)]
+#[cfg_attr(feature = "uniffi", derive(uniffi::Error))]
 pub enum EntropyError {
 	/// The given seed bytes are invalid, e.g., have invalid length.
 	InvalidSeedBytes,