[POC V1] T6.3 Add motion and polish pass

[fcarucci]

Imported from docs/milestones/proof-of-concept-1/poc_v1_task_breakdown.md.

Phase: P6 Error Handling And Polish

Source task: T6.3

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Purpose:

• hit the "beautiful diagram with nice graphics" bar

Output:

• motion tuning, hover states, empty-state art direction, polished gradients and shadows

Tests:

• manual QA checklist: desktop and mobile both feel polished
• visual regression snapshots for the main dashboard state
• visual regression snapshots for loading, empty, degraded, and success states

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