Fixed: #2034

feat(proxy): centralize proxy handling with `proxyutil` package and enhance test coverage

- Added `proxyutil` package to simplify proxy handling across the codebase.
- Refactored various components (`executor`, `cliproxy`, `auth`, etc.) to use `proxyutil` for consistent and reusable proxy logic.
- Introduced support for "direct" proxy mode to explicitly bypass all proxies.
- Updated tests to validate proxy behavior (e.g., `direct`, HTTP/HTTPS, and SOCKS5).
- Enhanced YAML configuration documentation for proxy options.

internal/api/handlers/management/test_store_test.go

@@ -0,0 +1,49 @@
+package management
+
+import (
+	"context"
+	"sync"
+
+	coreauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
+)
+
+type memoryAuthStore struct {
+	mu    sync.Mutex
+	items map[string]*coreauth.Auth
+}
+
+func (s *memoryAuthStore) List(_ context.Context) ([]*coreauth.Auth, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	out := make([]*coreauth.Auth, 0, len(s.items))
+	for _, item := range s.items {
+		out = append(out, item)
+	}
+	return out, nil
+}
+
+func (s *memoryAuthStore) Save(_ context.Context, auth *coreauth.Auth) (string, error) {
+	if auth == nil {
+		return "", nil
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if s.items == nil {
+		s.items = make(map[string]*coreauth.Auth)
+	}
+	s.items[auth.ID] = auth
+	return auth.ID, nil
+}
+
+func (s *memoryAuthStore) Delete(_ context.Context, id string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	delete(s.items, id)
+	return nil
+}
+
+func (s *memoryAuthStore) SetBaseDir(string) {}