refactor(verify-era-proof-attestation): modularize and restructure proof verification logic

- Split `verify-era-proof-attestation` into modular subcomponents for maintainability.
- Moved client, proof handling, and core types into dedicated modules.

bin/verify-era-proof-attestation/src/error.rs

@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (c) 2023-2025 Matter Labs
+
+//! Error types for the verification process
+
+use teepot::sgx::QuoteError;
+use thiserror::Error;
+use zksync_basic_types::L1BatchNumber;
+
+/// Result type used throughout the application
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Error types that can occur during verification
+#[derive(Error, Debug)]
+pub enum Error {
+    /// Error fetching proof
+    #[error("Failed to fetch proof for batch {batch_number}: {reason}")]
+    ProofFetch {
+        /// Batch number that caused the error
+        batch_number: L1BatchNumber,
+        /// Reason for the error
+        reason: String,
+    },
+
+    /// Error communicating with the HTTP server
+    #[error("HTTP request failed with status {status_code}: {message}")]
+    Http {
+        /// HTTP status code
+        status_code: u16,
+        /// Error message
+        message: String,
+    },
+
+    /// Error communicating with the JSON-RPC server
+    #[error("JSON-RPC error: {0}")]
+    JsonRpc(String),
+
+    /// JSON-RPC response has an invalid format
+    #[error("JSON-RPC response has an invalid format")]
+    JsonRpcInvalidResponse(String),
+
+    /// Invalid batch range
+    #[error("Invalid batch range: {0}")]
+    InvalidBatchRange(String),
+
+    /// Error verifying attestation
+    #[error(transparent)]
+    AttestationVerification(#[from] QuoteError),
+
+    /// Error verifying signature
+    #[error("Signature verification failed: {0}")]
+    SignatureVerification(String),
+
+    /// Attestation policy violation
+    #[error("Attestation policy violation: {0}")]
+    PolicyViolation(String),
+
+    /// Operation interrupted
+    #[error("Operation interrupted")]
+    Interrupted,
+
+    #[error(transparent)]
+    FromHex(#[from] hex::FromHexError),
+
+    /// Internal error
+    #[error("Internal error: {0}")]
+    Internal(String),
+}
+
+/// Utility functions for working with errors
+impl Error {
+    /// Create a new proof fetch error
+    pub fn proof_fetch(batch_number: L1BatchNumber, reason: impl Into<String>) -> Self {
+        Self::ProofFetch {
+            batch_number,
+            reason: reason.into(),
+        }
+    }
+
+    /// Create a new policy violation error
+    pub fn policy_violation(reason: impl Into<String>) -> Self {
+        Self::PolicyViolation(reason.into())
+    }
+
+    /// Create a new signature verification error
+    pub fn signature_verification(reason: impl Into<String>) -> Self {
+        Self::SignatureVerification(reason.into())
+    }
+
+    /// Create a new internal error
+    pub fn internal(reason: impl Into<String>) -> Self {
+        Self::Internal(reason.into())
+    }
+}
+
+impl From<reqwest::Error> for Error {
+    fn from(value: reqwest::Error) -> Self {
+        Self::Http {
+            status_code: value.status().map(|v| v.as_u16()).unwrap_or(0),
+            message: value.to_string(),
+        }
+    }
+}