Implement warning/announcement banner

[bryantran24]

Display a warning banner on the front page similar to the banner shown on https://shuttles.rpi.edu.

The app should fetch announcements from the JSON API endpoint: "https://api-shuttles.rpi.edu/api/announcements"

Example API Response from Shubble

{
    "announcements": [
        {
            "id": "chasan-weekday-hours",
            "message": "Chasan stop is only available M-F 7am-5:30pm. [View RPI Shuttle Info](https://administration.rpi.edu/parking-transportation/rensselaer-shuttle)",
            "type": "info",
            "active": true,
            "expiresAt": "2026-12-31T23:59:59"
        },
        {
            "id": "snow-days",
            "message": "Shuttles will not run or run with limited capacity until the weather improves",
            "type": "warning",
            "active": true,
            "expiresAt": "2026-1-28T23:59:59"
        }
    ]
}

Behavior

The banner behavior should follow these rules (or something else if you come up with something better):

• If an active announcement with type: "warning" exists, display the first warning in the warning banner.
• If no active warning exists, display the first active announcement with type: "info".
• If no active announcements exist, do not display a banner.

The features of the banner are:

• Displaying an announcement message.
• Be tappable navigating the user to the existing Announcements page using a > to maybe indicate that it is tappable.
• Be dismissible from the screen like an x or something.
• Announcement page should be accessible via Settings.

If message contains a Markdown-style link e.g. ... [View RPI Shuttle Info](https://...), parse the string into plain text + link text/URL and render it as clickable inline text in Jetpack Compose. For link rendering, see: https://developer.android.com/develop/ui/compose/text/user-interactions#create-clickable-text.

Dependencies

This feature depends on Shubble implementing the announcements API route.
This issue cannot be completed until that API is available.