fix(api): restore DefaultConfig() and constants used by config loader

- Restore api.DefaultConfig() - used by internal/config/loader.go
- Restore DefaultInterface, DefaultPort, DefaultBPFFilter constants
- Restore DefaultFlowTimeout, DefaultPacketBuffer constants
- Remove unused LogLevel* constants (never referenced in codebase)

docs(architecture.yml): update packaging and service sections

- Update packaging tool from fpm to rpmbuild
- Remove CentOS 7 / RHEL 7 from target distros (EOL)
- Update rpm_builder stage description for rpmbuild workflow
- Add spec_file section with version_macro documentation
- Update service to run as root (required for packet capture)
- Update security sandboxing to match current systemd unit
- Remove pid_file (not used)
- Update binary_path from /usr/local/bin to /usr/bin

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

api/types.go

@@ -232,3 +232,31 @@ func NewLogRecord(ch TLSClientHello, fp *Fingerprints) LogRecord {
 
 	return rec
 }
+
+// Default values and constants
+
+const (
+	DefaultInterface    = "eth0"
+	DefaultPort         = 443
+	DefaultBPFFilter    = ""
+	DefaultFlowTimeout  = 30 // seconds
+	DefaultPacketBuffer = 1000 // packet channel buffer size
+)
+
+// DefaultConfig returns an AppConfig with sensible default values.
+// Uses eth0 as the default interface, port 443 for monitoring,
+// no BPF filter, a 30-second flow timeout, and a 1000-packet
+// channel buffer. Returns an empty outputs slice (caller must
+// configure outputs explicitly).
+func DefaultConfig() AppConfig {
+	return AppConfig{
+		Core: Config{
+			Interface:        DefaultInterface,
+			ListenPorts:      []uint16{DefaultPort},
+			BPFFilter:        DefaultBPFFilter,
+			FlowTimeoutSec:   DefaultFlowTimeout,
+			PacketBufferSize: DefaultPacketBuffer,
+		},
+		Outputs: []OutputConfig{},
+	}
+}