Add LIVE Now section at the top of Places panel to match web

## Context

The web Places page now has a **LIVE Now** section at the top showing up to four scenes with active users (ordered by user count, highest first, no minimum threshold). The Explorer client currently shows all places in a single list with featured first, so scenes with many active users can appear below the entire featured shelf.

Kim requested parity between web and in-world:
> "ahh in explorer we don't have a LIVE at the top. Can talk to Nico about that (to match web)"
> "for example, .Make's stack has more people in it right now but its below all of the featured. Can we update in world to match that web design where live is at the top?"

## Requirements

- Add a **LIVE Now** horizontal section at the top of the Explore/Places panel, above Featured.
- Show up to 4 scenes with active users, ordered left-to-right by highest user count.
- No minimum user threshold — any scene with at least 1 user qualifies.
- Cards should show the LIVE badge (already supported via `PlaceCardView`).
- Deduplicate: scenes in LIVE Now should not repeat in Featured or the general grid (web uses feature flag `dapps-places-repeat-cross-sections` for this).
- Design assistance needed to match web aesthetics in the Explorer UI.

## Web reference

- Web implementation: [sites#815 — New Live Now behavior and event badges](https://github.com/decentraland/sites/pull/815)
- Live page: https://decentraland.org/places

## Data source

The `/destinations` API already returns `user_count` and `connected_addresses` per place. Explorer already reads these fields in [`PlaceCardView.cs#L159`](https://github.com/decentraland/unity-explorer/blob/6549cdd2adcf22d6387b68d393944b6bfcb28501/Explorer/Assets/DCL/Places/PlaceCardView.cs#L159).

## Screenshot (Nico's mockup)

Nico shared an early mockup showing the LIVE section above Featured in the Explorer panel — see the Slack thread for the screenshot.

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From Slack thread: https://decentralandteam.slack.com/archives/C0BCKT77XPS/p1788400010570959