mobile: message links not tappable / openable (works on desktop)

**Describe the bug**
In the Buzz **mobile app** (Android), hyperlinks in channel messages do **not** appear to work the way they do on **desktop**. On desktop, links in messages are clickable and open correctly; on mobile they do not behave as usable links (not opening / not clearly tappable).

Reported by an end user (ChrisV) comparing the same conversation across desktop vs Android.

**Steps to reproduce**
1. Open Buzz **desktop** and a channel thread that contains a normal HTTPS URL in a message (e.g. a GitHub PR link such as `https://github.com/cvolkernick/personal-workspace/pull/14`).
2. Confirm the link is clickable and opens in a browser.
3. Open the **same message** in the Buzz **Android** app.
4. Attempt to tap / open the same link.

**Expected behavior**
Mobile should render message links as tappable and open them (external browser or in-app browser), consistent with desktop markdown/link handling.

**Actual behavior**
Links do not work on mobile the way they do on desktop (user report: "Links do not appear to be working on the mobile app like they do on desktop").

**Version and platform**
- Buzz version: unknown (reporter can add from Settings if available on mobile)
- OS: Android
- Desktop: works (contrast platform)
- Relay / community context: managed Buzz community usage (not required to repro if link rendering is client-side)

**Logs / additional context**
- Client surface: Flutter mobile app under `mobile/` in this monorepo.
- Likely area: markdown / rich text link handling in mobile message render path (vs desktop).
- Not a duplicate of invite-link / pairing URL bugs (#3211, #3357, #4198) — this is **in-message content links** in normal channel chat.
- Happy to add screenshots, exact Android build version, and a sample event ID if maintainers need them.

**Source**
Filed from a Buzz #general thread after comparing desktop vs Android behavior on the same PR URL.