[Bug/Enhancement] Improve Login Verification Reliability

### The Issue
Occasionally, after entering credentials and clicking "Log In," the bot stays stuck on the `[INFO] Verifying authentication...` step and eventually times out. This happens even if the browser visually successfully loads the Instagram Home Feed.

This suggests our current success indicators (checking for the `Home Icon` or `Profile Avatar`) are sometimes too specific or slow to appear due to Instagram's UI variations (A/B testing) or network lag.

### The Goal
Make the login verification logic "bulletproof" by checking for a wider range of success indicators.

### Recommended Changes
Update the verification loop in `src/instagram.rs` to check for *any* of the following elements to confirm success:
1. **Alternative Icons:** Add checks for the "Search", "Reels", "Explore", or "Direct Message" icons.
2. **Navigation Bar:** Check for the existence of the bottom (mobile) or side (desktop) navigation `nav` element.
3. **Onboarding Modals:** Add detection for other common interruptions like "Turn on Notifications" or "Connect to Facebook" popups (treating them as a successful login).

### File to Edit
- `src/instagram.rs` (Inside the `login` function)