feat: initial VRRP implementation with health checking

- VRRP protocol implementation (RFC 3768/5798)
- Virtual IP management (add/remove VIPs)
- State machine (INIT/BACKUP/MASTER/FAULT)
- Priority-based master election
- Gratuitous ARP for network updates
- Health checking (TCP, HTTP, ICMP, Script)
- Configuration hot-reload (SIGHUP)

🤖 Generated with [Qoder][https://qoder.com]

etc/config.mini.yaml

@@ -0,0 +1,14 @@
+global:
+  router_id: "node1"
+
+vrrp_instances:
+  - name: "VI_1"
+    interface: "eth0"
+    state: "BACKUP"
+    virtual_router_id: 51
+    priority: 100
+    advert_interval: 1
+    auth_type: "PASS"
+    auth_pass: "secret123"
+    virtual_ips:
+      - "192.168.1.100/24"