feat(worker): 实现集群限流与自适应负载

保留平台模型 RPM、TPM 和并发策略语义，增加 PostgreSQL 集群级租约、饱和候选重选和多平台自动负载，避免突发任务固定等待首个平台。\n\n新增 Worker 实时负载采样、自适应 active/heavy 容量、心跳与管理端指标，并扩展本地 acceptance runner，覆盖三 Worker、同模型三平台 2/4/6 并发和 48 个带图视频突发任务。\n\n验证：go test ./...、go vet ./...、PostgreSQL 跨 Store 集成测试、gofmt、bash -n、ShellCheck 及本地集群 provider-burst 验收通过；48/48 成功，无越限、重复提交、重复计费、重复回调或终态资源泄漏。

apps/api/internal/acceptanceemulator/server_test.go

@@ -155,6 +155,44 @@ func TestForcedConversionRejectsImagesOutsideOfficialSeedanceRange(t *testing.T)
 	}
 }
 
+func TestGeminiProtocolAcceptsMultipleFileDataImages(t *testing.T) {
+	server := New(Config{Wait: func(context.Context, time.Duration) error { return nil }})
+	httpServer := httptest.NewServer(server.Handler())
+	defer httpServer.Close()
+	parts := []any{map[string]any{"text": "combine references"}}
+	for index := 0; index < 3; index++ {
+		parts = append(parts, map[string]any{"fileData": map[string]any{
+			"mimeType": "image/png",
+			"fileUri":  fmt.Sprintf("https://fixtures.example/%d.png", index),
+		}})
+	}
+	body, _ := json.Marshal(map[string]any{
+		"contents":         []any{map[string]any{"parts": parts}},
+		"generationConfig": map[string]any{"responseModalities": []any{"IMAGE"}},
+	})
+	response, err := postIdempotent(httpServer.URL+"/v1beta/models/gemini-test:generateContent", body, "gemini-multi")
+	if err != nil {
+		t.Fatalf("Gemini multi-image request: %v", err)
+	}
+	defer response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		payload, _ := io.ReadAll(response.Body)
+		t.Fatalf("Gemini multi-image status=%d body=%s", response.StatusCode, payload)
+	}
+	reportResponse, err := http.Get(httpServer.URL + "/report")
+	if err != nil {
+		t.Fatalf("get report: %v", err)
+	}
+	defer reportResponse.Body.Close()
+	var report Report
+	if err := json.NewDecoder(reportResponse.Body).Decode(&report); err != nil {
+		t.Fatalf("decode report: %v", err)
+	}
+	if report.GeminiRequests != 1 || report.GeminiInputImages != 3 || report.GeminiInvalid != 0 {
+		t.Fatalf("unexpected multi-image report: %+v", report)
+	}
+}
+
 func TestImageFixturesFullyDecode(t *testing.T) {
 	for name, fixture := range buildFixtures() {
 		if !strings.HasPrefix(fixture.ContentType, "image/") {