Add Direct Issue Link to Each Featured Issue Card

### 📋 Description

On the Recommendations page, the **"Good First Issues"** section shows issue cards with a title, AI summary, labels, and a "View on GitHub" button. However, the button links to the **repository's issues list** (`/issues`) rather than the **specific issue** itself.

The `Issue` interface already has a concept of individual issue data (title, body, labels), and since the `repoId` is available, a direct issue URL can be constructed. This makes the feature significantly more useful — users can go directly to the issue they want to work on.

---

### 📍 File to Change

`frontend/app/(auth)/recommendations/components/featuredissues.tsx`

---

### 🔍 Current Code (line ~87)

```tsx
window.open(`https://github.com/${repoId}/issues`, '_blank')}
// ← Links to entire issues list, not a specific issue
>

View on GitHub

```

---

### ✅ What To Do

**Step 1:** Update the `Issue` interface in `frontend/lib/api/core-service.ts` to include an `issue_number` field (if not already present):

```ts
export interface Issue {
title: string;
body: string;
labels: string[];
issue_number?: number; // ← add this
ai?: {
summary?: string;
difficulty?: string;
estimated_time?: string;
};
}
```

**Step 2:** In `featuredissues.tsx`, construct the direct issue URL when `issue_number` is available:

```tsx
const issueUrl = issue.issue_number
? `https://github.com/${repoId}/issues/${issue.issue_number}`
: `https://github.com/${repoId}/issues`;

// Then use it in the button:
onClick={() => window.open(issueUrl, '_blank')}
```

**Step 3:** Update the button label to reflect whether it's a direct link:

```tsx
{issue.issue_number ? `View Issue #${issue.issue_number}` : 'View Issues'}
```

---

### 🏁 Acceptance Criteria

- [ ] Each issue card's button links to the **specific issue** (e.g. `github.com/owner/repo/issues/42`) when an `issue_number` is available
- [ ] Falls back to the general issues list (`github.com/owner/repo/issues`) when `issue_number` is not present
- [ ] The `Issue` interface in `core-service.ts` has an optional `issue_number` field
- [ ] The button label changes accordingly (e.g. `"View Issue #42"` vs `"View Issues"`)

---

### 💡 Technical Hints

- The `repoId` prop is already passed to `FeaturedIssues` (it's the `owner/repo` string like `"vercel/next.js"`)
- GitHub issue URLs follow the pattern: `https://github.com/{owner}/{repo}/issues/{number}`
- The `issue_number` may or may not be returned by the backend — the interface change should be backward-compatible using `?` (optional)

---

### 🚀 Getting Started

1. Fork the repository
2. Create a branch: `git checkout -b fix/issue-17-direct-issue-links`
3. Edit `frontend/app/(auth)/recommendations/components/featuredissues.tsx`
4. Optionally update `frontend/lib/api/core-service.ts` to add `issue_number`
5. Run: `cd frontend && npm run dev` → go to `/recommendations`
6. Open a Pull Request!

Start with frontend/app/(auth)/recommendations/components/featuredissues.tsx and inspect how each Issue card builds its GitHub link and label. Check frontend/lib/api/core-service.ts for the Issue interface, then run the frontend development server and verify that cards with issue_number link to the specific issue while others use the repository issues list.

Written by the indexing model from the issue text.