Implement alert batching feature (Issue #22)

[Lexicoding-systems]

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Summary

Implements batch action functionality for escalation management to reduce notification fatigue and improve workflow efficiency.

Changes Made

• Batch Action Bar: Fixed bottom bar with slide-up animation that appears when escalations are selected
• Multi-Select UI: Added checkboxes to escalation cards for batch selection
• Batch Operations:
  • Batch approve escalations
  • Batch mark for review
  • Clear all selections
• Visual Feedback: Selected cards highlight with primary color and overlay
• Mock Data: Added 3 sample escalations with varying priorities and SLA status for demonstration
• Stats Integration: Updated escalation stats to show count and SLA violations

CSS Features

• @keyframes slideUp animation for smooth batch bar appearance
• Selected card styling with rgba(8, 145, 178, 0.15) background
• Checkbox styling with accent-color: var(--primary)
• Fixed positioning with z-index management

JavaScript Functions

• toggleEscalationSelection(id) - Handle checkbox state changes
• updateBatchActionBar() - Show/hide bar based on selection count
• updateEscalationCardStyles() - Apply visual feedback to selected cards
• batchApproveEscalations() - Approve selected items (API ready)
• batchReviewEscalations() - Mark for review (API ready)
• clearBatchSelection() - Reset all selections

API Integration Points

The batch operations include commented API call examples for production:

await fetch(`${API_BASE}/api/governance/escalations/batch-approve`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ escalation_ids: ids })
});

Test Plan

1. Open governance dashboard
2. Verify 3 escalations are displayed with checkboxes
3. Select one or more escalations
4. Verify batch action bar appears with correct count
5. Click "Approve All" - verify success toast
6. Verify selections clear after batch operation
7. Test "Mark for Review" and "Clear" buttons
8. Verify SLA violation indicator on critical escalation

Resolves

Closes #22

🤖 Generated with Claude Code
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