feat(frontend): add user activity timeline with chronological history and user isolation

frontend/src/app/(dashboard)/user/overview/page.tsx

@@ -1,12 +1,32 @@
 "use client";
 
-import React from "react";
+import React, { useState, useEffect } from "react";
 import ActiveGroupsWidget from "./components/ActiveGroupsWidget";
 import ContributorProfileCard from "./components/ContributorProfileCard";
+import { UserActivityTimeline } from "@/components/UserActivityTimeline";
 import { motion } from "framer-motion";
 import { LayoutDashboard } from "lucide-react";
+import { getPublicKey } from "@/hooks/stellar-wallets-kit";
 
 export default function OverviewPage() {
+  const [walletAddress, setWalletAddress] = useState<string | null>(null);
+
+  useEffect(() => {
+    let cancelled = false;
+
+    async function checkWallet() {
+      const key = await getPublicKey();
+      if (!cancelled) {
+        setWalletAddress(key ?? "demo-user");
+      }
+    }
+
+    void checkWallet();
+    return () => {
+      cancelled = true;
+    };
+  }, []);
+
   return (
     <div className="w-full">
       {/* Page Header */}
@@ -24,14 +44,15 @@ export default function OverviewPage() {
             Overview
           </h1>
           <p className="text-[#5A6578] text-xs sm:text-sm font-medium mt-0.5">
-            Welcome back — here&apos;s a snapshot of your groups
+            Welcome back — here&apos;s a snapshot of your groups & activities
           </p>
         </div>
       </motion.div>
 
       {/* Widgets Grid */}
       <div className="grid grid-cols-1 lg:grid-cols-1 gap-6 sm:gap-8">
         <ContributorProfileCard />
+        <UserActivityTimeline userId={walletAddress} />
         <ActiveGroupsWidget />
       </div>
     </div>

frontend/src/app/api/activities/route.ts

@@ -0,0 +1,141 @@
+import { buildNoStoreJson } from "@/lib/api-response";
+import { checkRateLimit } from "@/lib/rate-limit";
+import {
+  listUserActivities,
+  recordActivity,
+  seedDefaultActivitiesIfEmpty,
+} from "@/lib/activity-store";
+import type { ActivityType } from "@/types/activity";
+
+export const runtime = "nodejs";
+export const dynamic = "force-dynamic";
+
+export async function GET(request: Request) {
+  const { response: rateLimitResponse, headers: rateLimitHeaders } =
+    checkRateLimit(request);
+  if (rateLimitResponse) {
+    return rateLimitResponse;
+  }
+
+  const { searchParams } = new URL(request.url);
+  const userId = (searchParams.get("userId") ?? "").trim();
+
+  if (!userId) {
+    return buildNoStoreJson(
+      {
+        ok: false,
+        error: "userId query parameter is required.",
+      },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  // Seed default activities for demo user if none exist yet
+  seedDefaultActivitiesIfEmpty(userId);
+
+  const type = (searchParams.get("type") as ActivityType) || undefined;
+  const limitParam = searchParams.get("limit");
+  const offsetParam = searchParams.get("offset");
+
+  const limit = limitParam ? parseInt(limitParam, 10) : 50;
+  const offset = offsetParam ? parseInt(offsetParam, 10) : 0;
+
+  const result = listUserActivities({
+    userId,
+    type,
+    limit,
+    offset,
+  });
+
+  return buildNoStoreJson(
+    {
+      ok: true,
+      activities: result.activities,
+      total: result.total,
+    },
+    200,
+    rateLimitHeaders,
+  );
+}
+
+export async function POST(request: Request) {
+  const { response: rateLimitResponse, headers: rateLimitHeaders } =
+    checkRateLimit(request);
+  if (rateLimitResponse) {
+    return rateLimitResponse;
+  }
+
+  let body: unknown;
+  try {
+    body = await request.json();
+  } catch {
+    return buildNoStoreJson(
+      {
+        ok: false,
+        error: "Request body must be valid JSON.",
+      },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  if (!body || typeof body !== "object") {
+    return buildNoStoreJson(
+      {
+        ok: false,
+        error: "Invalid activity payload.",
+      },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  const payload = body as Record<string, unknown>;
+  const userId = String(payload.userId ?? "").trim();
+  const type = String(payload.type ?? "") as ActivityType;
+  const title = String(payload.title ?? "").trim();
+  const description = String(payload.description ?? "").trim();
+  const metadata = (payload.metadata ?? undefined) as Record<string, unknown> | undefined;
+
+  if (!userId) {
+    return buildNoStoreJson(
+      { ok: false, error: "userId is required." },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  if (!type) {
+    return buildNoStoreJson(
+      { ok: false, error: "type is required." },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  if (!title) {
+    return buildNoStoreJson(
+      { ok: false, error: "title is required." },
+      400,
+      rateLimitHeaders,
+    );
+  }
+
+  const activity = recordActivity({
+    userId,
+    type,
+    title,
+    description,
+    metadata,
+  });
+
+  return buildNoStoreJson(
+    {
+      ok: true,
+      activity,
+    },
+    201,
+    rateLimitHeaders,
+  );
+}