fix(frontend): 修复重构时遗漏的 SVG 图标，创建统一图标管理组件

- 创建 Icon.vue 统一管理 SVG 图标（20+ 常用图标）
- 修复 AccountActionMenu 中被错误替换为 emoji 的图标
- 修复 ProfileView 和 GroupsView 中的 emoji 图标
- 图标支持 size/strokeWidth 属性，便于复用

backend/internal/service/antigravity_gateway_service.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"log"
+	mathrand "math/rand"
 	"net/http"
 	"strings"
 	"sync/atomic"
@@ -405,6 +406,14 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 	// 重试循环
 	var resp *http.Response
 	for attempt := 1; attempt <= antigravityMaxRetries; attempt++ {
+		// 检查 context 是否已取消（客户端断开连接）
+		select {
+		case <-ctx.Done():
+			log.Printf("%s status=context_canceled error=%v", prefix, ctx.Err())
+			return nil, ctx.Err()
+		default:
+		}
+
 		upstreamReq, err := antigravity.NewAPIRequest(ctx, action, accessToken, geminiBody)
 		if err != nil {
 			return nil, err
@@ -414,7 +423,10 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		if err != nil {
 			if attempt < antigravityMaxRetries {
 				log.Printf("%s status=request_failed retry=%d/%d error=%v", prefix, attempt, antigravityMaxRetries, err)
-				sleepAntigravityBackoff(attempt)
+				if !sleepAntigravityBackoffWithContext(ctx, attempt) {
+					log.Printf("%s status=context_canceled_during_backoff", prefix)
+					return nil, ctx.Err()
+				}
 				continue
 			}
 			log.Printf("%s status=request_failed retries_exhausted error=%v", prefix, err)
@@ -427,7 +439,10 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 
 			if attempt < antigravityMaxRetries {
 				log.Printf("%s status=%d retry=%d/%d", prefix, resp.StatusCode, attempt, antigravityMaxRetries)
-				sleepAntigravityBackoff(attempt)
+				if !sleepAntigravityBackoffWithContext(ctx, attempt) {
+					log.Printf("%s status=context_canceled_during_backoff", prefix)
+					return nil, ctx.Err()
+				}
 				continue
 			}
 			// 所有重试都失败，标记限流状态
@@ -901,6 +916,14 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 	// 重试循环
 	var resp *http.Response
 	for attempt := 1; attempt <= antigravityMaxRetries; attempt++ {
+		// 检查 context 是否已取消（客户端断开连接）
+		select {
+		case <-ctx.Done():
+			log.Printf("%s status=context_canceled error=%v", prefix, ctx.Err())
+			return nil, ctx.Err()
+		default:
+		}
+
 		upstreamReq, err := antigravity.NewAPIRequest(ctx, upstreamAction, accessToken, wrappedBody)
 		if err != nil {
 			return nil, err
@@ -910,7 +933,10 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 		if err != nil {
 			if attempt < antigravityMaxRetries {
 				log.Printf("%s status=request_failed retry=%d/%d error=%v", prefix, attempt, antigravityMaxRetries, err)
-				sleepAntigravityBackoff(attempt)
+				if !sleepAntigravityBackoffWithContext(ctx, attempt) {
+					log.Printf("%s status=context_canceled_during_backoff", prefix)
+					return nil, ctx.Err()
+				}
 				continue
 			}
 			log.Printf("%s status=request_failed retries_exhausted error=%v", prefix, err)
@@ -923,7 +949,10 @@ func (s *AntigravityGatewayService) ForwardGemini(ctx context.Context, c *gin.Co
 
 			if attempt < antigravityMaxRetries {
 				log.Printf("%s status=%d retry=%d/%d", prefix, resp.StatusCode, attempt, antigravityMaxRetries)
-				sleepAntigravityBackoff(attempt)
+				if !sleepAntigravityBackoffWithContext(ctx, attempt) {
+					log.Printf("%s status=context_canceled_during_backoff", prefix)
+					return nil, ctx.Err()
+				}
 				continue
 			}
 			// 所有重试都失败，标记限流状态
@@ -1062,6 +1091,30 @@ func sleepAntigravityBackoff(attempt int) {
 	sleepGeminiBackoff(attempt) // 复用 Gemini 的退避逻辑
 }
 
+// sleepAntigravityBackoffWithContext 带 context 取消检查的退避等待
+// 返回 true 表示正常完成等待，false 表示 context 已取消
+func sleepAntigravityBackoffWithContext(ctx context.Context, attempt int) bool {
+	delay := geminiRetryBaseDelay * time.Duration(1<<uint(attempt-1))
+	if delay > geminiRetryMaxDelay {
+		delay = geminiRetryMaxDelay
+	}
+
+	// +/- 20% jitter
+	r := mathrand.New(mathrand.NewSource(time.Now().UnixNano()))
+	jitter := time.Duration(float64(delay) * 0.2 * (r.Float64()*2 - 1))
+	sleepFor := delay + jitter
+	if sleepFor < 0 {
+		sleepFor = 0
+	}
+
+	select {
+	case <-ctx.Done():
+		return false
+	case <-time.After(sleepFor):
+		return true
+	}
+}
+
 func (s *AntigravityGatewayService) handleUpstreamError(ctx context.Context, prefix string, account *Account, statusCode int, headers http.Header, body []byte) {
 	// 429 使用 Gemini 格式解析（从 body 解析重置时间）
 	if statusCode == 429 {