feat(api): wire server configuration and dependencies

backend/cmd/api/config_test.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestReadConfigUsesDefaults(t *testing.T) {
+	values := map[string]string{
+		"ZARINHUB_ACCESS_TOKEN": "test-token",
+	}
+
+	config, err := readConfig(func(key string) string {
+		return values[key]
+	})
+	if err != nil {
+		t.Fatalf("readConfig() error = %v", err)
+	}
+
+	if config.ServerAddr != "127.0.0.1:8080" {
+		t.Errorf("ServerAddr = %q", config.ServerAddr)
+	}
+	if config.FrontendOrigin != "http://127.0.0.1:3000" {
+		t.Errorf("FrontendOrigin = %q", config.FrontendOrigin)
+	}
+	if config.ZarinHubTimeout != 5*time.Second {
+		t.Errorf("ZarinHubTimeout = %v", config.ZarinHubTimeout)
+	}
+	if config.DatabasePath != "./card-to-iban.db" {
+		t.Errorf("DatabasePath = %q", config.DatabasePath)
+	}
+}
+
+func TestReadConfigRejectsMissingAccessToken(t *testing.T) {
+	_, err := readConfig(func(key string) string { return "" })
+	if err == nil || !strings.Contains(err.Error(), "ZARINHUB_ACCESS_TOKEN") {
+		t.Fatalf("readConfig() error = %v, want missing token error", err)
+	}
+}
+
+func TestReadConfigRejectsInvalidTimeout(t *testing.T) {
+	values := map[string]string{
+		"ZARINHUB_ACCESS_TOKEN": "test-token",
+		"ZARINHUB_TIMEOUT":      "later",
+	}
+
+	_, err := readConfig(func(key string) string {
+		return values[key]
+	})
+	if err == nil || !strings.Contains(err.Error(), "ZARINHUB_TIMEOUT") {
+		t.Fatalf("readConfig() error = %v, want timeout error", err)
+	}
+}