feat: Remove unused imports and suppress dead_code warnings across charging engine modules

- Remove unused AsyncCommands/error/ChargingSession/ErrorContext imports from credit_management
- Remove unused ErrorContext/ChargingError imports from engine
- Remove unused ErrorContext import from rating_billing and prefix unused variables with underscore
- Remove unused ErrorContext import from rating_plans_repo
- Remove unused Context import from errors/helpers
- Remove unused info/debug/SystemTime imports from monitoring
- Remove unused sleep

apps/charging-engine/src/charging/credit_management.rs

@@ -1,8 +1,7 @@
-use redis::AsyncCommands;
-use tracing::{info, warn, error, debug};
+use tracing::{info, warn, debug};
 
-use super::types::{SubscriberAccount, UsageEvent, ChargingSession};
-use crate::errors::{ChargingError, ChargingResult, ErrorContext, validate_imsi, validate_session_id, validate_bytes};
+use super::types::{SubscriberAccount, UsageEvent};
+use crate::errors::{ChargingError, ChargingResult, validate_imsi, validate_session_id};
 
 impl crate::charging::ChargingEngine {
     pub async fn get_balance(&self, ip: &str) -> ChargingResult<u64> {

apps/charging-engine/src/charging/engine.rs

@@ -4,7 +4,7 @@ use tracing::info;
 
 use super::rating_plans_repo::RatingPlansRepo;
 use super::types::RatingPlan;
-use crate::errors::{ChargingResult, ErrorContext, ChargingError};
+use crate::errors::ChargingResult;
 
 /// ChargingEngine coordinates Redis-backed hot-path state (balances, sessions)
 /// and Postgres-backed configuration (rating plans) via `RatingPlansRepo`.

apps/charging-engine/src/charging/rating_billing.rs

@@ -2,13 +2,14 @@ use chrono::Utc;
 use tracing::{info, debug, warn};
 
 use super::types::{UsageEvent, UsageType};
-use crate::errors::{ChargingError, ChargingResult, ErrorContext, validate_amount};
+use crate::errors::{ChargingError, ChargingResult, validate_amount};
 
+#[allow(dead_code)]
 impl super::ChargingEngine {
     pub async fn calculate_usage_cost(&self, event: &UsageEvent) -> ChargingResult<f64> {
         // Get subscriber account to determine rating plan
         let account = self.get_subscriber_account(&event.imsi).await?;
-        let account = account.ok_or_else(|| ChargingError::SubscriberNotFound(event.imsi.clone()))?;
+        let _account = account.ok_or_else(|| ChargingError::SubscriberNotFound(event.imsi.clone()))?;
 
         // Get rating plan from Postgres (simplified - defaults to basic).
         let plan = self
@@ -128,7 +129,7 @@ impl super::ChargingEngine {
         Ok(())
     }
 
-    pub async fn generate_invoice(&self, imsi: &str, billing_period: &str) -> ChargingResult<f64> {
+    pub async fn generate_invoice(&self, imsi: &str, _billing_period: &str) -> ChargingResult<f64> {
         // Get all usage events for the billing period
         let mut conn = self.redis_client.get_multiplexed_async_connection().await
             .map_err(|e| crate::errors::ChargingError::RedisConnection(e.to_string()))?;

apps/charging-engine/src/charging/rating_plans_repo.rs

@@ -9,7 +9,7 @@ use sqlx::postgres::{PgPool, PgPoolOptions};
 use sqlx::Row;
 
 use super::types::RatingPlan;
-use crate::errors::{ChargingError, ChargingResult, ErrorContext};
+use crate::errors::ChargingResult;
 
 /// Repository for rating plans backed by Postgres.
 #[derive(Clone)]

apps/charging-engine/src/charging/types.rs

@@ -56,6 +56,7 @@ pub struct RatingPlan {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
 pub struct ChargingSession {
     pub session_id: String,
     pub imsi: String,
@@ -69,6 +70,7 @@ pub struct ChargingSession {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
 pub enum SessionStatus {
     Active,
     Completed,
@@ -76,6 +78,7 @@ pub enum SessionStatus {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
 pub struct ChargingRule {
     pub rule_id: String,
     pub name: String,
@@ -85,6 +88,7 @@ pub struct ChargingRule {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
 pub struct Condition {
     pub field: String,
     pub operator: String,
@@ -92,6 +96,7 @@ pub struct Condition {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[allow(dead_code)]
 pub struct Action {
     pub action_type: String,
     pub parameters: std::collections::HashMap<String, String>,

apps/charging-engine/src/errors/helpers.rs

@@ -1,4 +1,3 @@
-use anyhow::Context;
 
 use super::types::ChargingError;
 

apps/charging-engine/src/errors/types.rs

@@ -10,9 +10,11 @@ pub enum ChargingError {
     SubscriberNotFound(String),
     RatingPlanNotFound(String),
     InsufficientCredit { available: u64, requested: u64 },
+    #[allow(dead_code)]
     UsageBlocked(String),
     InvalidInput(String),
     SerializationError(String),
+    #[allow(dead_code)]
     ConfigurationError(String),
     InternalError(String),
 }

apps/charging-engine/src/models.rs

@@ -1,6 +1,7 @@
 use serde::{Deserialize, Serialize};
 
 #[derive(Clone)]
+#[allow(dead_code)]
 pub struct AppState {
     pub charging_engine: std::sync::Arc<crate::charging::ChargingEngine>,
 }

apps/charging-engine/src/monitoring/monitoring.rs

@@ -1,8 +1,5 @@
-use tracing::{info, debug};
-use std::time::SystemTime;
 
-use crate::errors::{ChargingError, ChargingResult, ErrorContext};
-use super::types::{SystemStats, HealthStatus};
+use crate::errors::ChargingResult;
 
 impl crate::charging::ChargingEngine {
     pub async fn get_performance_metrics(&self) -> ChargingResult<PerformanceMetrics> {

apps/charging-engine/src/monitoring/sync.rs

@@ -1,9 +1,8 @@
-use tokio::time::{interval, sleep};
+use tokio::time::interval;
 use tracing::{info, warn, error, debug};
-use std::time::Duration;
 use chrono::Datelike;
 
-use crate::errors::{ChargingError, ChargingResult, ErrorContext, log_error};
+use crate::errors::{ChargingResult, log_error};
 use crate::monitoring::types::{SystemStats, HealthStatus};
 
 impl crate::charging::ChargingEngine {

apps/charging-engine/src/monitoring/types.rs

@@ -16,6 +16,7 @@ pub struct HealthStatus {
 }
 
 #[derive(Debug, Clone)]
+#[allow(dead_code)]
 pub struct PerformanceMetrics {
     pub connected_clients: u64,
     pub used_memory: u64,
@@ -25,6 +26,7 @@ pub struct PerformanceMetrics {
 }
 
 #[derive(Debug, Clone)]
+#[allow(dead_code)]
 pub struct ErrorStats {
     pub total_errors: u64,
     pub error_types: std::collections::HashMap<String, u64>,