Show Full Date for "Last Checked" in the Profile Watchlist

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In the **Profile page → Watched Repositories** section, each watched repo shows a "Last checked" timestamp. Currently, it is rendered using `.toLocaleTimeString()` which only shows the time — for example: `"3:45:02 PM"`.

If a repo was last checked yesterday, 3 days ago, or last week, the user sees no date context at all — just a meaningless time like `"11:30:00 AM"`. This is confusing and unhelpful.

---

### 📍 File to Change

`frontend/app/(auth)/profile/page.tsx` — inside the `Watchlist` sub-component (around line 271)

---

### 🔍 Current Code (line ~271)

```tsx


Last checked: {repo.last_checked_at
? new Date(repo.last_checked_at).toLocaleTimeString() // ← PROBLEM: no date!
: 'Never'}

```

---

### ✅ What To Do

**Option A (Recommended) — Relative time** (e.g., `"2 hours ago"`, `"3 days ago"`):

Add a `formatTimeAgo` helper (already exists in `notifications/page.tsx` — you can copy it into `frontend/lib/utils.ts` to share it):

```ts
// In frontend/lib/utils.ts
export function formatTimeAgo(date: Date): string {
const seconds = Math.floor((new Date().getTime() - date.getTime()) / 1000);
if (seconds < 60) return `${seconds}s ago`;
const minutes = Math.floor(seconds / 60);
if (minutes < 60) return `${minutes}m ago`;
const hours = Math.floor(minutes / 60);
if (hours < 24) return `${hours}h ago`;
const days = Math.floor(hours / 24);
return `${days}d ago`;
}
```

Then use it:
```tsx
Last checked: {repo.last_checked_at
? formatTimeAgo(new Date(repo.last_checked_at))
: 'Never'}
```

**Option B — Full locale string:**
```tsx
Last checked: {repo.last_checked_at
? new Date(repo.last_checked_at).toLocaleString() // Shows date + time
: 'Never'}
```

Either option is acceptable — relative time (Option A) is preferred.

---

### 🏁 Acceptance Criteria

- [ ] "Last checked" in the Watchlist section of the Profile page shows date context (relative or full date+time)
- [ ] If `last_checked_at` is `null`, it still shows `"Never"`
- [ ] The change is inside the `Watchlist` component in `profile/page.tsx`
- [ ] (Bonus) The `formatTimeAgo` helper is extracted to `frontend/lib/utils.ts` and imported in both `profile/page.tsx` and `notifications/page.tsx`

---

### 💡 Technical Hints

- The bug is at line ~271 in `frontend/app/(auth)/profile/page.tsx` — find `.toLocaleTimeString()` and replace it
- The `formatTimeAgo` function already exists in `frontend/app/(auth)/notifications/page.tsx` — no need to write it from scratch, just move it to a shared utility

---

### 🚀 Getting Started

1. Fork the repository
2. Create a branch: `git checkout -b fix/issue-6-watchlist-date-format`
3. Edit `frontend/app/(auth)/profile/page.tsx`
4. Optionally, extract `formatTimeAgo` to `frontend/lib/utils.ts`
5. Run locally: `cd frontend && npm run dev` → navigate to `/profile`
6. Open a Pull Request!

Start in frontend/app/(auth)/profile/page.tsx, inside the Watchlist component, and inspect the .toLocaleTimeString() call. Compare the existing formatTimeAgo helper in frontend/app/(auth)/notifications/page.tsx, then run cd frontend && npm run dev and visit /profile. Done means Last checked includes date context while null values still display “Never”.

Written by the indexing model from the issue text.