feat(app): add WGRplane web UI and backend features

- Add Vue 3 frontend with glassmorphism design (Tailwind CSS)
- Add Go backend handlers: auth, webhooks, stats, scheduler, validation
- Add i18n support (EN, ID, ZH)
- Add Swagger docs and API handlers
- Add nftables integration and plugins support
- Remove deprecated go.mod (migrated to wgrplane)

app/validation.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+    "encoding/base64"
+    "net"
+)
+
+// ValidateIP returns true if the input is a valid IPv4 or IPv6 address.
+func ValidateIP(ip string) bool {
+    if ip == "" {
+        return false
+    }
+    return net.ParseIP(ip) != nil
+}
+
+// ValidateCIDR returns true if the input is a valid CIDR notation (e.g., 10.0.0.0/24).
+func ValidateCIDR(cidr string) bool {
+    if cidr == "" {
+        return false
+    }
+    // net.ParseCIDR validates CIDR; it also returns an IP, which we don't need here.
+    if _, _, err := net.ParseCIDR(cidr); err != nil {
+        return false
+    }
+    return true
+}
+
+// ValidatePublicKey returns true if the provided WireGuard public key is a valid base64-encoded 32-byte value.
+func ValidatePublicKey(key string) bool {
+    if key == "" {
+        return false
+    }
+    // Try to decode as base64 without padding (RawStdEncoding).
+    if b, err := base64.RawStdEncoding.DecodeString(key); err == nil && len(b) == 32 {
+        return true
+    }
+    // Fallback to standard base64 decoding with padding if present.
+    if b, err := base64.StdEncoding.DecodeString(key); err == nil && len(b) == 32 {
+        return true
+    }
+    return false
+}