fix: resolve all linting errors

- Use typed context key instead of string in errorbus test to avoid collisions
- Remove unused imports (health.HealthChecker, trace.TracerProvider) from test files
- Simplify interface verification checks (removed unnecessary type assertions)

All linting errors resolved. make lint now passes.

internal/errorbus/channel_bus_test.go

@@ -106,7 +106,9 @@ func TestChannelBus_Publish_WithContext(t *testing.T) {
 	bus := NewChannelBus(mockLogger, 10)
 
 	testErr := errors.New("test error")
-	ctx := context.WithValue(context.Background(), "request_id", "test-request-id")
+	type contextKey string
+	const requestIDKey contextKey = "request_id"
+	ctx := context.WithValue(context.Background(), requestIDKey, "test-request-id")
 
 	bus.Publish(ctx, testErr)