feat: explorer API, wallet, CCIP scripts, and config refresh

- Backend REST/gateway/track routes, analytics, Blockscout proxy paths.
- Frontend wallet and liquidity surfaces; MetaMask token list alignment.
- Deployment docs, verification scripts, address inventory updates.

Check: go build ./... under backend/ (pass).
Made-with: Cursor

backend/api/track4/endpoints_test.go

@@ -0,0 +1,63 @@
+package track4
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestHandleValidatorsRejectsNonGET(t *testing.T) {
+	server := NewServer(nil, 138)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/track4/operator/validators", nil)
+	w := httptest.NewRecorder()
+
+	server.HandleValidators(w, req)
+
+	if w.Code != http.StatusMethodNotAllowed {
+		t.Fatalf("expected 405 for non-GET validators request, got %d", w.Code)
+	}
+}
+
+func TestHandleContractsRequiresDatabase(t *testing.T) {
+	server := NewServer(nil, 138)
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/track4/operator/contracts", nil)
+	w := httptest.NewRecorder()
+
+	server.HandleContracts(w, req)
+
+	if w.Code != http.StatusServiceUnavailable {
+		t.Fatalf("expected 503 when track4 DB is missing, got %d", w.Code)
+	}
+}
+
+func TestLoadContractRegistryReadsConfiguredFile(t *testing.T) {
+	tempDir := t.TempDir()
+	registryPath := filepath.Join(tempDir, "smart-contracts-master.json")
+	err := os.WriteFile(registryPath, []byte(`{
+	  "chains": {
+	    "138": {
+	      "contracts": {
+	        "CCIP_ROUTER": "0x1111111111111111111111111111111111111111",
+	        "CHAIN138_BRIDGE": "0x2222222222222222222222222222222222222222"
+	      }
+	    }
+	  }
+	}`), 0o644)
+	if err != nil {
+		t.Fatalf("failed to write temp registry: %v", err)
+	}
+
+	t.Setenv("SMART_CONTRACTS_MASTER_JSON", registryPath)
+	entries, err := loadContractRegistry(138)
+	if err != nil {
+		t.Fatalf("loadContractRegistry returned error: %v", err)
+	}
+	if len(entries) != 2 {
+		t.Fatalf("expected 2 registry entries, got %d", len(entries))
+	}
+	if entries[0].Type == "" || entries[1].Type == "" {
+		t.Fatal("expected contract types to be inferred")
+	}
+}