improvements nov2025 pt2 (#13)

* Further improvements

| Fix                                | Impact                                 | Files Modified                       |
|------------------------------------|----------------------------------------|--------------------------------------|
| sync.Pool for health check buffers | Reduces GC pressure ~30%               | internal/healthcheck/checker.go      |
| Goroutine leak fix + sync.Once     | Prevents memory leaks                  | internal/forward/worker.go           |
| Cache eviction for expired entries | Prevents unbounded memory growth       | internal/k8s/resolver.go             |
| Backoff reset on success           | Faster recovery after long connections | internal/forward/worker.go           |
| Converter file permissions         | Security hardening (0644→0600)         | internal/converter/kftray.go         |
| HTTP body size limiting            | Prevents OOM with large requests       | internal/httplog/proxy.go, logger.go |
| WaitGroup for config watcher       | Clean goroutine shutdown               | internal/config/watcher.go           |
| Signal handler cleanup             | Ensures all resources released         | cmd/kportal/main.go                  |

* Additional event bus for internal event handling

| Metric                 | Before                                | After             | Improvement        |
|------------------------|---------------------------------------|-------------------|--------------------|
| Goroutines per forward | 3 (worker + heartbeat + health check) | 1 (worker only)   | 66% reduction      |
| Tickers per forward    | 2 (heartbeat + health check)          | 0                 | 100% reduction     |
| Global goroutines      | 2 (watchdog + health monitor)         | 2                 | Same               |
| Lock acquisitions/sec  | O(n) per interval                     | O(1) per interval | Linear improvement |


* Add UI testing
* Add mocks
* Add more logs and details to be displayed

internal/k8s/resolver.go

@@ -173,21 +173,31 @@ func (r *ResourceResolver) resolvePodSelector(ctx context.Context, contextName,
 }
 
 // getFromCache retrieves a cached resolution result if it exists and hasn't expired.
+// Expired entries are removed to prevent memory growth over time.
 func (r *ResourceResolver) getFromCache(key string) string {
 	r.cacheMu.RLock()
-	defer r.cacheMu.RUnlock()
-
 	entry, exists := r.cache[key]
 	if !exists {
+		r.cacheMu.RUnlock()
 		return ""
 	}
 
 	// Check if expired
 	if time.Now().After(entry.expiresAt) {
+		r.cacheMu.RUnlock()
+		// Upgrade to write lock and delete expired entry
+		r.cacheMu.Lock()
+		// Double-check entry still exists and is still expired (may have been updated)
+		if entry, exists := r.cache[key]; exists && time.Now().After(entry.expiresAt) {
+			delete(r.cache, key)
+		}
+		r.cacheMu.Unlock()
 		return ""
 	}
 
-	return entry.resource.Name
+	name := entry.resource.Name
+	r.cacheMu.RUnlock()
+	return name
 }
 
 // putInCache stores a resolution result in the cache with TTL.