Add `SenderDashboard` with stream creation history and analytics

[ritik4ever]

Problem

SenderDashboard.tsx exists but may be a stub. Senders have no dedicated analytics view showing their total streamed amount, active streams, and history.

Scope

Build out SenderDashboard with aggregate stats fetched from /api/stats and /api/streams?sender=<address>.

Acceptance criteria

• Cards: total streams created, total amount streamed, active streams, completed streams
• Bar chart: streams by status
• Recent activity feed: last 10 events from /api/events?sender=<address>
• Quick action buttons: Create Stream, Bulk Cancel
• Vitest test renders with mocked API data

Complexity: Medium · 150 points

[espcris05-commits]

/attempt #392

I'd like to add SenderDashboard with stream creation history and analytics.

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