refactor: Extract health checks and utility modules from packet-gateway ebpf module

- Extract health check handlers to new health.rs module (health, liveness, readiness, metrics endpoints)
- Extract IP conversion utilities to new ip_utils.rs module (u32_to_ipv4_string, ipv4_string_to_u32)
- Extract Redis synchronization logic to new redis_sync.rs module (RedisSyncer with sync_packet_stats, sync_credit_info, sync_credits_from_redis, sync_blocked_from_redis, sync_batch_entry methods)
- Refactor EbpfManager

apps/packet-gateway/src/ip_utils.rs

@@ -0,0 +1,15 @@
+use anyhow::{Context, Result};
+use std::net::Ipv4Addr;
+
+/// Converts a u32 IP address to an IPv4 string
+pub fn u32_to_ipv4_string(ip: u32) -> String {
+    let ip_addr = Ipv4Addr::from(ip);
+    ip_addr.to_string()
+}
+
+/// Converts an IPv4 string to a u32 IP address
+pub fn ipv4_string_to_u32(ip_str: &str) -> Result<u32> {
+    let ip_addr: Ipv4Addr = ip_str.parse()
+        .context("Invalid IP address format")?;
+    Ok(u32::from(ip_addr))
+}