Add static/moving camera toggle with S

[Hartwich]

Goal

Add a host camera mode toggle for Magic Arena.

Codex Auftrag

Press S on the host screen to toggle between static camera mode and moving camera mode.

Focus

• static mode keeps current camera behavior
• moving mode follows the currently acting figure
• look roughly toward the target field or action direction
• keep the board readable
• avoid motion sickness by using smooth transitions

Acceptance Criteria

• S toggles camera mode only on the host.
• Static mode keeps the current camera behavior.
• Moving mode follows the acting figure during action resolution.
• Current mode is visible in development or documented.
• npm run typecheck passes.
• npm run build passes.

Safety

Do not add copyrighted, unclear, or unreviewed third-party assets or content.