feat(network): add protocol packet capture and replay system

Add a recording and replay foundation for the MHF network protocol.
A RecordingConn decorator wraps network.Conn to transparently capture
all decrypted packets to binary .mhfr files, with zero handler changes
and zero overhead when disabled.

- network/pcap: binary capture format (writer, reader, filters)
- RecordingConn: thread-safe Conn decorator with direction tracking
- CaptureOptions in config (disabled by default)
- Capture wired into all three server types (sign, entrance, channel)
- cmd/replay: CLI tool with dump, json, stats, and compare modes
- 19 new tests, all passing with -race

config/config.go

@@ -85,6 +85,7 @@ type Config struct {
 	EarthMonsters          []int32
 	SaveDumps              SaveDumpOptions
 	Screenshots            ScreenshotsOptions
+	Capture                CaptureOptions
 
 	DebugOptions    DebugOptions
 	GameplayOptions GameplayOptions
@@ -112,6 +113,16 @@ type ScreenshotsOptions struct {
 	UploadQuality int //Determines the upload quality to the server
 }
 
+// CaptureOptions controls protocol packet capture recording.
+type CaptureOptions struct {
+	Enabled         bool     // Enable packet capture
+	OutputDir       string   // Directory for .mhfr capture files
+	ExcludeOpcodes  []uint16 // Opcodes to exclude from capture (e.g., ping, nop, position)
+	CaptureSign     bool     // Capture sign server sessions
+	CaptureEntrance bool     // Capture entrance server sessions
+	CaptureChannel  bool     // Capture channel server sessions
+}
+
 // DebugOptions holds various debug/temporary options for use while developing Erupe.
 type DebugOptions struct {
 	CleanDB             bool   // Automatically wipes the DB on server reset.
@@ -328,6 +339,12 @@ func LoadConfig() (*Config, error) {
 		Enabled:   true,
 		OutputDir: "save-backups",
 	})
+	viper.SetDefault("Capture", CaptureOptions{
+		OutputDir:       "captures",
+		CaptureSign:     true,
+		CaptureEntrance: true,
+		CaptureChannel:  true,
+	})
 	viper.SetDefault("LoopDelay", 50)
 
 	err := viper.ReadInConfig()