Restructure audit package and remove Reason field

- Split audit.go into separate files:
  - request.go: Request struct and HTTPRequestToAuditRequest function
  - logging_auditor.go: LoggingAuditor implementation and Auditor interface
- Move LoggingAuditor tests to logging_auditor_test.go
- Keep general audit tests (HTTPRequestToAuditRequest) in request_test.go
- Remove Request.Reason field and ReasonNoMatchingRules constant
- Update proxy to use concrete LoggingAuditor type instead of interface
- Simplify audit logging by removing reason parameter from DENY logs
- All tests pass with improved organization and cleaner API

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: f0ssel

audit/audit.go

@@ -0,0 +1,29 @@
+package audit
+
+import "log/slog"
+
+// LoggingAuditor implements Auditor by logging to slog
+type LoggingAuditor struct {
+	logger *slog.Logger
+}
+
+// NewLoggingAuditor creates a new LoggingAuditor
+func NewLoggingAuditor(logger *slog.Logger) *LoggingAuditor {
+	return &LoggingAuditor{
+		logger: logger,
+	}
+}
+
+// AuditRequest logs the request using structured logging
+func (a *LoggingAuditor) AuditRequest(req *Request) {
+	if req.Allowed {
+		a.logger.Info("ALLOW",
+			"method", req.Method,
+			"url", req.URL,
+			"rule", req.Rule)
+	} else {
+		a.logger.Warn("DENY",
+			"method", req.Method,
+			"url", req.URL)
+	}
+}