feat: implement ntfy-discord bridge in Go

- SSE subscription to ntfy with auto-reconnect
- Discord webhook integration with embed formatting
- Priority to color mapping, tag to emoji conversion
- Native HashiCorp Vault support (Kubernetes + token auth)
- Hot reload secrets via fsnotify or Vault polling
- Prometheus metrics (/metrics endpoint)
- Health/ready endpoints for Kubernetes probes
- Comprehensive unit tests and fuzz tests
- Multi-stage Docker build (~10MB scratch image)
- CI/CD pipeline for Gitea Actions

internal/config/fuzz_test.go

@@ -0,0 +1,72 @@
+package config
+
+import (
+	"testing"
+)
+
+// FuzzParseTopics tests topic parsing doesn't panic on arbitrary input
+func FuzzParseTopics(f *testing.F) {
+	// Normal cases
+	f.Add("alerts")
+	f.Add("alerts,updates")
+	f.Add("alerts, updates, notifications")
+	f.Add("")
+
+	// Edge cases
+	f.Add(",,,")
+	f.Add("  ,  ,  ")
+	f.Add("a]topic-with-special_chars.123")
+	f.Add("\x00\x00\x00")
+	f.Add("topic\nwith\nnewlines")
+
+	f.Fuzz(func(t *testing.T, input string) {
+		// Simulate topic parsing logic
+		if input == "" {
+			return
+		}
+
+		topics := make([]string, 0)
+		for _, topic := range splitAndTrim(input) {
+			topics = append(topics, topic)
+		}
+
+		// Accessing results should not panic
+		_ = len(topics)
+	})
+}
+
+// splitAndTrim mimics the topic parsing in Load()
+func splitAndTrim(s string) []string {
+	if s == "" {
+		return nil
+	}
+	var result []string
+	start := 0
+	for i := 0; i < len(s); i++ {
+		if s[i] == ',' {
+			part := trimSpace(s[start:i])
+			if part != "" {
+				result = append(result, part)
+			}
+			start = i + 1
+		}
+	}
+	// Last part
+	part := trimSpace(s[start:])
+	if part != "" {
+		result = append(result, part)
+	}
+	return result
+}
+
+func trimSpace(s string) string {
+	start := 0
+	end := len(s)
+	for start < end && (s[start] == ' ' || s[start] == '\t' || s[start] == '\n' || s[start] == '\r') {
+		start++
+	}
+	for end > start && (s[end-1] == ' ' || s[end-1] == '\t' || s[end-1] == '\n' || s[end-1] == '\r') {
+		end--
+	}
+	return s[start:end]
+}