[shadowmap] feat: responsive dashboard exports

[mdabir1203]

Summary

• persist dashboard scans to disk, expose the export path in the UI, and allow opening the folder directly from the Slint surface
• refresh the premium theme tokens and orchestrator controls while adapting stats, activity, alerts, and timeline panels to stack on compact widths
• add the open crate dependency so the desktop build can launch the export directory cross-platform

Testing

• cargo fmt --all
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• cargo check --features dashboard

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https://chatgpt.com/codex/tasks/task_e_68eb398792a083268e4408e475f72488