完成产品审查剩余修复：新手指引、反馈入口、付费墙预览

P1-4：新增 WelcomeOverlay 新手指引
- 首次访问时显示 3 步引导：①从地图选城市 ②查看城市简报 ③解锁 Pro 深入分析
- 圆点进度指示、跳过/下一步按钮、点背景可关闭
- 看过一次后 localStorage 标记不再显示

P1-5：付费墙增加功能预览
- HistoryModal 在付费墙上方展示功能说明文案
- 新增 i18n 键 history.previewTitle / history.previewDesc（中英双语）

P2-9：新增反馈入口
- 顶栏增加 Telegram 反馈按钮（MessageCircle 图标）
- 点击跳转 PolyWeather 社群

Tested: npx tsc --noEmit

frontend/components/dashboard/HistoryModal.tsx

@@ -92,7 +92,17 @@ export function HistoryModal() {
           </div>
         </div>
       ) : !isPro ? (
-        <ProFeaturePaywall feature="history" onClose={store.closeHistory} />
+        <>
+          <div className="modal-content" style={{ padding: "24px 28px 0", textAlign: "center" }}>
+            <h3 style={{ fontSize: 18, fontWeight: 800, color: "var(--color-text-primary)", margin: "0 0 8px" }}>
+              {t("history.previewTitle")}
+            </h3>
+            <p style={{ fontSize: 13, color: "var(--color-text-secondary)", lineHeight: 1.6, margin: 0 }}>
+              {t("history.previewDesc")}
+            </p>
+          </div>
+          <ProFeaturePaywall feature="history" onClose={store.closeHistory} />
+        </>
       ) : (
         <div className="modal-content history-modal">
           <div className="modal-header">

frontend/components/dashboard/ScanTerminalDashboard.tsx

@@ -5,6 +5,7 @@ import dynamic from "next/dynamic";
 import Link from "next/link";
 import {
   LogIn,
+  MessageCircle,
   Moon,
   RefreshCw,
   Sun,
@@ -31,6 +32,7 @@ import type {
 } from "@/lib/dashboard-types";
 import { AiPinnedForecastView } from "@/components/dashboard/scan-terminal/AiPinnedForecastView";
 import { LoadingSignal } from "@/components/dashboard/scan-terminal/LoadingSignal";
+import { WelcomeOverlay } from "@/components/dashboard/scan-terminal/WelcomeOverlay";
 import { findDetailForCity } from "@/components/dashboard/scan-terminal/city-detail-utils";
 import {
   findRowForCity,
@@ -451,6 +453,16 @@ function ScanTerminalScreen() {
                   <UserRound size={15} />
                 </Link>
               ) : null}
+              <a
+                href="https://t.me/+nMG7SjziUKYyZmM1"
+                target="_blank"
+                rel="noopener noreferrer"
+                className="scan-account-button"
+                aria-label={isEn ? "Feedback" : "反馈"}
+                title={isEn ? "Join Telegram for feedback" : "加入 Telegram 反馈"}
+              >
+                <MessageCircle size={15} />
+              </a>
             </div>
           </div>
 
@@ -575,6 +587,7 @@ function ScanTerminalScreen() {
 
         <CityDetailPanel variant="rail" />
       </div>
+      <WelcomeOverlay locale={locale} onDismiss={() => {}} />
       <FutureForecastModal />
       {showScanPaywall ? (
         <div

frontend/components/dashboard/ScanTerminalState.module.css

@@ -314,3 +314,114 @@
     transform: scaleY(1);
   }
 }
+
+/* ── Welcome onboarding overlay ── */
+.root :global(.scan-welcome-overlay) {
+  position: fixed;
+  inset: 0;
+  z-index: 1000;
+  display: grid;
+  place-items: center;
+  background: rgba(2, 6, 23, 0.72);
+  backdrop-filter: blur(4px);
+  animation: fadeIn 0.25s ease;
+  padding: 24px;
+}
+
+.root :global(.scan-welcome-card) {
+  width: 100%;
+  max-width: 400px;
+  padding: 32px 28px 24px;
+  border: 1px solid rgba(77, 163, 255, 0.22);
+  border-radius: 24px;
+  background: linear-gradient(160deg, rgba(17, 26, 46, 0.98), rgba(11, 18, 32, 0.98));
+  box-shadow: 0 24px 80px rgba(0, 0, 0, 0.5);
+  text-align: center;
+  animation: fadeUpIn 0.3s ease;
+}
+
+.root :global(.scan-welcome-steps) {
+  display: flex;
+  justify-content: center;
+  gap: 8px;
+  margin-bottom: 20px;
+}
+
+.root :global(.scan-welcome-dot) {
+  width: 8px;
+  height: 8px;
+  border-radius: 999px;
+  background: rgba(77, 163, 255, 0.2);
+  transition: all 0.2s;
+}
+
+.root :global(.scan-welcome-dot.active) {
+  width: 24px;
+  background: var(--color-accent-primary);
+}
+
+.root :global(.scan-welcome-dot.done) {
+  background: rgba(77, 163, 255, 0.5);
+}
+
+.root :global(.scan-welcome-icon-wrap) {
+  width: 64px;
+  height: 64px;
+  margin: 0 auto 16px;
+  display: grid;
+  place-items: center;
+  border-radius: 18px;
+  background: rgba(77, 163, 255, 0.12);
+  border: 1px solid rgba(77, 163, 255, 0.18);
+}
+
+.root :global(.scan-welcome-icon) {
+  color: var(--color-accent-secondary);
+}
+
+.root :global(.scan-welcome-title) {
+  font-size: 20px;
+  font-weight: 800;
+  color: var(--color-text-primary);
+  margin: 0 0 8px;
+}
+
+.root :global(.scan-welcome-desc) {
+  font-size: 14px;
+  color: var(--color-text-secondary);
+  line-height: 1.6;
+  margin: 0 0 24px;
+}
+
+.root :global(.scan-welcome-actions) {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 12px;
+}
+
+.root :global(.scan-welcome-skip) {
+  border: none;
+  background: transparent;
+  color: var(--color-text-muted);
+  font-size: 13px;
+  font-weight: 600;
+  cursor: pointer;
+  padding: 8px 12px;
+  border-radius: 8px;
+  transition: color 0.15s;
+}
+
+.root :global(.scan-welcome-skip:hover) {
+  color: var(--color-text-secondary);
+}
+
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+@keyframes fadeUpIn {
+  from { opacity: 0; transform: translateY(12px); }
+  to { opacity: 1; transform: translateY(0); }
+}

frontend/components/dashboard/scan-terminal/WelcomeOverlay.tsx

@@ -0,0 +1,120 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { MapPin, FileText, Crown } from "lucide-react";
+
+const STORAGE_KEY = "polyweather_welcome_seen";
+
+type Props = {
+  locale: string;
+  onDismiss: () => void;
+};
+
+const steps = [
+  {
+    icon: MapPin,
+    titleEn: "Pick a city on the map",
+    titleZh: "从地图选城市",
+    descEn: "Click any colored bubble to view real-time weather and forecasts.",
+    descZh: "点击地图上的彩色气泡，查看实时天气和预报。",
+  },
+  {
+    icon: FileText,
+    titleEn: "Read the city briefing",
+    titleZh: "查看城市简报",
+    descEn: "The right panel shows current temperature, DEB forecast, and detailed metrics.",
+    descZh: "右侧面板展示当前温度、DEB 预报和各项指标。",
+  },
+  {
+    icon: Crown,
+    titleEn: "Unlock Pro for deep analysis",
+    titleZh: "解锁 Pro 深入分析",
+    descEn: "Pro unlocks AI-powered METAR reads, model evidence, market layer, and intraday analysis.",
+    descZh: "Pro 解锁 AI 机场报文解读、模型证据、市场层、日内分析。",
+  },
+];
+
+export function WelcomeOverlay({ locale, onDismiss }: Props) {
+  const [visible, setVisible] = useState(false);
+  const [step, setStep] = useState(0);
+  const isEn = locale === "en-US";
+
+  useEffect(() => {
+    const seen = localStorage.getItem(STORAGE_KEY);
+    if (!seen) {
+      setVisible(true);
+    }
+  }, []);
+
+  if (!visible) return null;
+
+  const current = steps[step];
+  const isLast = step === steps.length - 1;
+
+  const handleDismiss = () => {
+    localStorage.setItem(STORAGE_KEY, "1");
+    setVisible(false);
+    onDismiss();
+  };
+
+  const handleNext = () => {
+    if (isLast) {
+      handleDismiss();
+    } else {
+      setStep(step + 1);
+    }
+  };
+
+  return (
+    <div
+      className="scan-welcome-overlay"
+      role="dialog"
+      aria-label={isEn ? "Welcome guide" : "新手指引"}
+      onClick={handleDismiss}
+    >
+      <div
+        className="scan-welcome-card"
+        onClick={(e) => e.stopPropagation()}
+      >
+        <div className="scan-welcome-steps">
+          {steps.map((_, i) => (
+            <span
+              key={i}
+              className={`scan-welcome-dot ${i === step ? "active" : ""} ${i < step ? "done" : ""}`}
+            />
+          ))}
+        </div>
+
+        <div className="scan-welcome-icon-wrap">
+          <current.icon size={32} className="scan-welcome-icon" />
+        </div>
+
+        <h2 className="scan-welcome-title">
+          {isEn ? current.titleEn : current.titleZh}
+        </h2>
+        <p className="scan-welcome-desc">
+          {isEn ? current.descEn : current.descZh}
+        </p>
+
+        <div className="scan-welcome-actions">
+          <button
+            type="button"
+            className="scan-welcome-skip"
+            onClick={handleDismiss}
+          >
+            {isEn ? "Skip" : "跳过"}
+          </button>
+          <button
+            type="button"
+            className="scan-primary-button"
+            onClick={handleNext}
+          >
+            {isLast
+              ? isEn ? "Got it" : "知道了"
+              : isEn ? "Next" : "下一步"}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}

frontend/lib/i18n.ts

@@ -77,6 +77,8 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "history.loading": "正在获取历史数据...",
     "history.error": "获取历史信息失败",
     "history.empty": "近 15 天暂无该城市历史数据",
+    "history.previewTitle": "历史准确率对账",
+    "history.previewDesc": "对比 DEB 预报与实际结算温度，查看命中率、MAE 和模型对比。升级 Pro 即可解锁。",
     "history.hitRate": "DEB 结算胜率 (METAR)",
     "history.mae": "DEB MAE",
     "history.debHitRate": "DEB 结算胜率 (METAR)",
@@ -274,6 +276,8 @@ const MESSAGES: Record<Locale, Record<string, string>> = {
     "history.loading": "Loading historical data...",
     "history.error": "Failed to load historical data",
     "history.empty": "No historical records for this city in the last 15 days",
+    "history.previewTitle": "Historical Reconciliation",
+    "history.previewDesc": "Compare DEB forecasts to actual settlement temperatures with hit rate, MAE, and model comparison. Unlock Pro to access.",
     "history.hitRate": "DEB Settlement Hit Rate (METAR)",
     "history.mae": "DEB MAE",
     "history.debHitRate": "DEB Settlement Hit Rate (METAR)",