merge: 合并官方 upstream/main 的 6 个功能更新

合并内容：
1. feat(gateway): Claude Code 系统提示词智能注入
2. fix: 修复创建账号 schedulable 默认值为 false 的 bug
3. fix(frontend): 修复跨时区日期范围筛选问题
4. feat(proxy): SOCKS5H 代理支持（统一代理配置）
5. fix(oauth): 修复 Claude Cookie 添加账号时会话混淆
6. fix(test): 修复 OAuth 账号测试刷新 token 的 bug

新增文件：
- backend/internal/pkg/proxyutil/* (SOCKS5H 支持)
- backend/internal/service/gateway_prompt_test.go (测试)

来自 upstream: Wei-Shaw/sub2api commits d9b1587..a527559

backend/internal/service/gateway_prompt_test.go

@@ -0,0 +1,233 @@
+package service
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsClaudeCodeClient(t *testing.T) {
+	tests := []struct {
+		name           string
+		userAgent      string
+		metadataUserID string
+		want           bool
+	}{
+		{
+			name:           "Claude Code client",
+			userAgent:      "claude-cli/1.0.62 (darwin; arm64)",
+			metadataUserID: "session_123e4567-e89b-12d3-a456-426614174000",
+			want:           true,
+		},
+		{
+			name:           "Claude Code without version suffix",
+			userAgent:      "claude-cli/2.0.0",
+			metadataUserID: "session_abc",
+			want:           true,
+		},
+		{
+			name:           "Missing metadata user_id",
+			userAgent:      "claude-cli/1.0.0",
+			metadataUserID: "",
+			want:           false,
+		},
+		{
+			name:           "Different user agent",
+			userAgent:      "curl/7.68.0",
+			metadataUserID: "user123",
+			want:           false,
+		},
+		{
+			name:           "Empty user agent",
+			userAgent:      "",
+			metadataUserID: "user123",
+			want:           false,
+		},
+		{
+			name:           "Similar but not Claude CLI",
+			userAgent:      "claude-api/1.0.0",
+			metadataUserID: "user123",
+			want:           false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := isClaudeCodeClient(tt.userAgent, tt.metadataUserID)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestSystemIncludesClaudeCodePrompt(t *testing.T) {
+	tests := []struct {
+		name   string
+		system any
+		want   bool
+	}{
+		{
+			name:   "nil system",
+			system: nil,
+			want:   false,
+		},
+		{
+			name:   "empty string",
+			system: "",
+			want:   false,
+		},
+		{
+			name:   "string with Claude Code prompt",
+			system: claudeCodeSystemPrompt,
+			want:   true,
+		},
+		{
+			name:   "string with different content",
+			system: "You are a helpful assistant.",
+			want:   false,
+		},
+		{
+			name:   "empty array",
+			system: []any{},
+			want:   false,
+		},
+		{
+			name: "array with Claude Code prompt",
+			system: []any{
+				map[string]any{
+					"type": "text",
+					"text": claudeCodeSystemPrompt,
+				},
+			},
+			want: true,
+		},
+		{
+			name: "array with Claude Code prompt in second position",
+			system: []any{
+				map[string]any{"type": "text", "text": "First prompt"},
+				map[string]any{"type": "text", "text": claudeCodeSystemPrompt},
+			},
+			want: true,
+		},
+		{
+			name: "array without Claude Code prompt",
+			system: []any{
+				map[string]any{"type": "text", "text": "Custom prompt"},
+			},
+			want: false,
+		},
+		{
+			name: "array with partial match (should not match)",
+			system: []any{
+				map[string]any{"type": "text", "text": "You are Claude"},
+			},
+			want: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := systemIncludesClaudeCodePrompt(tt.system)
+			require.Equal(t, tt.want, got)
+		})
+	}
+}
+
+func TestInjectClaudeCodePrompt(t *testing.T) {
+	tests := []struct {
+		name           string
+		body           string
+		system         any
+		wantSystemLen  int
+		wantFirstText  string
+		wantSecondText string
+	}{
+		{
+			name:          "nil system",
+			body:          `{"model":"claude-3"}`,
+			system:        nil,
+			wantSystemLen: 1,
+			wantFirstText: claudeCodeSystemPrompt,
+		},
+		{
+			name:          "empty string system",
+			body:          `{"model":"claude-3"}`,
+			system:        "",
+			wantSystemLen: 1,
+			wantFirstText: claudeCodeSystemPrompt,
+		},
+		{
+			name:           "string system",
+			body:           `{"model":"claude-3"}`,
+			system:         "Custom prompt",
+			wantSystemLen:  2,
+			wantFirstText:  claudeCodeSystemPrompt,
+			wantSecondText: "Custom prompt",
+		},
+		{
+			name:          "string system equals Claude Code prompt",
+			body:          `{"model":"claude-3"}`,
+			system:        claudeCodeSystemPrompt,
+			wantSystemLen: 1,
+			wantFirstText: claudeCodeSystemPrompt,
+		},
+		{
+			name:   "array system",
+			body:   `{"model":"claude-3"}`,
+			system: []any{map[string]any{"type": "text", "text": "Custom"}},
+			// Claude Code + Custom = 2
+			wantSystemLen:  2,
+			wantFirstText:  claudeCodeSystemPrompt,
+			wantSecondText: "Custom",
+		},
+		{
+			name: "array system with existing Claude Code prompt (should dedupe)",
+			body: `{"model":"claude-3"}`,
+			system: []any{
+				map[string]any{"type": "text", "text": claudeCodeSystemPrompt},
+				map[string]any{"type": "text", "text": "Other"},
+			},
+			// Claude Code at start + Other = 2 (deduped)
+			wantSystemLen:  2,
+			wantFirstText:  claudeCodeSystemPrompt,
+			wantSecondText: "Other",
+		},
+		{
+			name:          "empty array",
+			body:          `{"model":"claude-3"}`,
+			system:        []any{},
+			wantSystemLen: 1,
+			wantFirstText: claudeCodeSystemPrompt,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := injectClaudeCodePrompt([]byte(tt.body), tt.system)
+
+			var parsed map[string]any
+			err := json.Unmarshal(result, &parsed)
+			require.NoError(t, err)
+
+			system, ok := parsed["system"].([]any)
+			require.True(t, ok, "system should be an array")
+			require.Len(t, system, tt.wantSystemLen)
+
+			first, ok := system[0].(map[string]any)
+			require.True(t, ok)
+			require.Equal(t, tt.wantFirstText, first["text"])
+			require.Equal(t, "text", first["type"])
+
+			// Check cache_control
+			cc, ok := first["cache_control"].(map[string]any)
+			require.True(t, ok)
+			require.Equal(t, "ephemeral", cc["type"])
+
+			if tt.wantSecondText != "" && len(system) > 1 {
+				second, ok := system[1].(map[string]any)
+				require.True(t, ok)
+				require.Equal(t, tt.wantSecondText, second["text"])
+			}
+		})
+	}
+}