refactor: harden sqlite runtime and packaged startup flow

- refine config loading with --config and current-directory .env

- improve sqlite busy handling and runtime DB tuning

- restore telegram payment notification and wallet input flow

- add behavior-based config and callback recovery tests

src/config/config_test.go

@@ -0,0 +1,118 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestNormalizeConfiguredPathUsesExplicitFile(t *testing.T) {
+	t.Helper()
+
+	root := t.TempDir()
+	configPath := filepath.Join(root, "custom.env")
+	if err := os.WriteFile(configPath, []byte("app_name=test\n"), 0o644); err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	got, err := normalizeConfiguredPath(configPath)
+	if err != nil {
+		t.Fatalf("normalize explicit file: %v", err)
+	}
+	if got != configPath {
+		t.Fatalf("config path = %s, want %s", got, configPath)
+	}
+}
+
+func TestNormalizeConfiguredPathUsesExplicitDirectory(t *testing.T) {
+	t.Helper()
+
+	root := t.TempDir()
+	configPath := filepath.Join(root, ".env")
+	if err := os.WriteFile(configPath, []byte("app_name=test\n"), 0o644); err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+
+	got, err := normalizeConfiguredPath(root)
+	if err != nil {
+		t.Fatalf("normalize explicit directory: %v", err)
+	}
+	if got != configPath {
+		t.Fatalf("config path = %s, want %s", got, configPath)
+	}
+}
+
+func TestResolveConfigFilePathUsesCurrentDirectoryByDefault(t *testing.T) {
+	t.Helper()
+
+	oldCwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("get cwd: %v", err)
+	}
+	defer func() { _ = os.Chdir(oldCwd) }()
+
+	root := t.TempDir()
+	configPath := filepath.Join(root, ".env")
+	if err := os.WriteFile(configPath, []byte("app_name=test\n"), 0o644); err != nil {
+		t.Fatalf("write config: %v", err)
+	}
+	if err := os.Chdir(root); err != nil {
+		t.Fatalf("chdir: %v", err)
+	}
+
+	t.Setenv("EPUSDT_CONFIG", "")
+	SetConfigPath("")
+
+	got, err := resolveConfigFilePath()
+	if err != nil {
+		t.Fatalf("resolve config path: %v", err)
+	}
+	if got != configPath {
+		t.Fatalf("config path = %s, want %s", got, configPath)
+	}
+}
+
+func TestResolveConfigFilePathPrefersExplicitOverEnv(t *testing.T) {
+	t.Helper()
+
+	oldCwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("get cwd: %v", err)
+	}
+	defer func() { _ = os.Chdir(oldCwd) }()
+
+	root := t.TempDir()
+	if err := os.Chdir(root); err != nil {
+		t.Fatalf("chdir: %v", err)
+	}
+
+	envDir := filepath.Join(root, "from-env")
+	if err := os.MkdirAll(envDir, 0o755); err != nil {
+		t.Fatalf("mkdir env dir: %v", err)
+	}
+	envPath := filepath.Join(envDir, ".env")
+	if err := os.WriteFile(envPath, []byte("app_name=env\n"), 0o644); err != nil {
+		t.Fatalf("write env config: %v", err)
+	}
+
+	flagDir := filepath.Join(root, "from-flag")
+	if err := os.MkdirAll(flagDir, 0o755); err != nil {
+		t.Fatalf("mkdir flag dir: %v", err)
+	}
+	flagPath := filepath.Join(flagDir, ".env")
+	if err := os.WriteFile(flagPath, []byte("app_name=flag\n"), 0o644); err != nil {
+		t.Fatalf("write flag config: %v", err)
+	}
+
+	t.Setenv("EPUSDT_CONFIG", envDir)
+	SetConfigPath(flagDir)
+	defer SetConfigPath("")
+
+	got, err := resolveConfigFilePath()
+	if err != nil {
+		t.Fatalf("resolve config path: %v", err)
+	}
+	if got != flagPath {
+		t.Fatalf("config path = %s, want %s", got, flagPath)
+	}
+}