feat: add responsive admin dashboard

[Itodo-S]

Summary

• add a responsive admin dashboard screen with merchant, subscription, user, analytics, and audit sections
• add a dashboard service layer with role-based controls, bulk operations, and seeded reporting data
• wire the dashboard into settings navigation and update shared card typing for responsive layouts

Closes #215

Verification

• local source review of the dashboard interactions and navigation wiring
• automated app and test commands were not runnable here because the project dependencies are not installed in this environment

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