feat(proxy): add proxy IP management and account routing

Add admin CRUD and connectivity checks for SOCKS5/SOCKS5H proxy nodes.

Allow accounts to bind to a proxy, route DeepSeek requests through the selected node, and expose proxy management in the admin UI.

internal/deepseek/proxy_test.go

@@ -0,0 +1,85 @@
+package deepseek
+
+import (
+	"context"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+func TestProxyDialAddressUsesLocalResolutionForSocks5(t *testing.T) {
+	ctx := context.Background()
+	resolved, err := proxyDialAddress(ctx, "socks5", "example.com:443", func(_ context.Context, network, host string) ([]string, error) {
+		if network != "ip" {
+			t.Fatalf("unexpected lookup network: %q", network)
+		}
+		if host != "example.com" {
+			t.Fatalf("unexpected lookup host: %q", host)
+		}
+		return []string{"203.0.113.10"}, nil
+	})
+	if err != nil {
+		t.Fatalf("proxyDialAddress returned error: %v", err)
+	}
+	if resolved != "203.0.113.10:443" {
+		t.Fatalf("expected locally resolved address, got %q", resolved)
+	}
+}
+
+func TestProxyDialAddressKeepsHostnameForSocks5h(t *testing.T) {
+	ctx := context.Background()
+	lookups := 0
+	resolved, err := proxyDialAddress(ctx, "socks5h", "example.com:443", func(_ context.Context, network, host string) ([]string, error) {
+		lookups++
+		return []string{"203.0.113.10"}, nil
+	})
+	if err != nil {
+		t.Fatalf("proxyDialAddress returned error: %v", err)
+	}
+	if resolved != "example.com:443" {
+		t.Fatalf("expected hostname preserved for remote DNS, got %q", resolved)
+	}
+	if lookups != 0 {
+		t.Fatalf("expected no local DNS lookup for socks5h, got %d", lookups)
+	}
+}
+
+func TestApplyProxyConnectivityHeadersUsesBaseHeaders(t *testing.T) {
+	req, err := http.NewRequest(http.MethodGet, "https://chat.deepseek.com/", nil)
+	if err != nil {
+		t.Fatalf("http.NewRequest returned error: %v", err)
+	}
+
+	applyProxyConnectivityHeaders(req)
+
+	for key, want := range BaseHeaders {
+		if got := req.Header.Get(key); got != want {
+			t.Fatalf("expected header %q=%q, got %q", key, want, got)
+		}
+	}
+}
+
+func TestProxyConnectivityStatus(t *testing.T) {
+	cases := []struct {
+		name       string
+		statusCode int
+		success    bool
+		wantText   string
+	}{
+		{name: "ok", statusCode: 200, success: true, wantText: "HTTP 200"},
+		{name: "challenge", statusCode: 403, success: true, wantText: "风控或挑战"},
+		{name: "upstream error", statusCode: 502, success: false, wantText: "HTTP 502"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			success, message := proxyConnectivityStatus(tc.statusCode)
+			if success != tc.success {
+				t.Fatalf("expected success=%v, got %v", tc.success, success)
+			}
+			if message == "" || !strings.Contains(message, tc.wantText) {
+				t.Fatalf("expected message to contain %q, got %q", tc.wantText, message)
+			}
+		})
+	}
+}