Fix/issues 509 512 514 517

[xeladev4]

Fix frontend debug logging, accessibility, dead code, and backend pagination

Summary

This PR addresses four issues spanning frontend UX improvements and backend API consistency:

• Removes debug console logging from SSE event handling and stream-detail page
• Removes unused users query parameter that the backend ignores
• Adds accessible ARIA label to the top-up amount input field
• Removes dead legacy Dashboard component with hardcoded mock data
• Adds page parameter support to the stream events endpoint for consistent pagination

Fixes

Closes #509
Closes #512
Closes #514
Closes #517

Changes

Frontend

Issue #509: Remove debug console logging and unused users param

• Removed console.log('SSE connected:', data.clientId) from useStreamEvents hook onmessage handler
• Removed console.error() calls from SSE message parsing
• Removed console.log() call from reconnect retry logic
• Removed unused users query parameter appended to SSE subscription URL
• Updated buildUrl dependency array to remove userPublicKeys

Issue #512: Add accessible label to top-up input

• Added aria-label="Top-up amount" to the number input field on stream detail page
• Maintains existing placeholder as a visual hint, not the sole accessible label
• No visual changes to the UI

Issue #514: Remove dead Dashboard component

• Deleted frontend/src/components/Dashboard.tsx which contained hardcoded mock stream data
• This was a legacy component not used by the application (live dashboard is at app/dashboard/page.tsx)

Backend

Issue #517: Add page parameter support

• Updated getStreamEvents controller to accept optional page query parameter
• Maps 1-based page number to offset: offset = (page - 1) * limit
• Page parameter is only used when offset and cursor are not provided
• Maintains full backward compatibility with existing offset/cursor-based pagination
• Mirrors the behavior of the sibling /v1/events endpoint

Test Plan

• Frontend builds successfully: cd frontend && npm run build
• Backend builds successfully: cd backend && npm run build
• Frontend lint passes: cd frontend && npm run lint
• Backend tests pass: cd backend && npm run test
• No console errors when stream-detail page loads
• Browser console shows no debug logs during SSE event updates
• Top-up input properly labeled in accessibility tools
• Stream event pagination works: /v1/streams/123/events?page=2&limit=10
• Backward compatibility: offset/cursor-based pagination still works

Architecture Notes

• No schema or API contract changes (page parameter is additive)
• User-scoped events continue to arrive via server-side user subscription
• Removed unused users parameter reduces noise in URL construction

Branch

fix/issues-509-512-514-517