Add error handling and validation to screenshot viewer

[Copilot]

The screenshot viewer in AdminPanel.tsx lacked error handling for base64 data processing, risking runtime crashes on invalid input and memory leaks from unreleased object URLs.

Changes

• Extracted handleViewScreenshot function from inline handler with try-catch-finally structure
• Validation chain:
  • Regex check (/^data:[^;]+;base64,/) for proper data URL format
  • Split validation before array access to prevent undefined
  • 10MB size limit on base64 data to prevent browser hangs
• Error recovery: Toast notifications with specific messages for different failure modes (missing data, invalid format, oversized payload, atob failure)
• Resource cleanup: URL.revokeObjectURL() in finally block with 1000ms delay for new window load

Before:

onClick={() => {
  const base64Data = number.screenshot?.split(',')[1];
  const byteCharacters = atob(base64Data || '');
  // ... direct blob creation and window.open, no error handling
}}

After:

onClick={() => handleViewScreenshot(number.screenshot)}

// Separate function with:
// - Pre-flight validation (format, size)
// - try-catch around atob/Blob operations
// - finally block ensuring URL cleanup
// - Toast feedback for all error paths

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Harden screenshot viewer: Add error handling for invalid base64 data</issue_title>
<issue_description>## Description

The screenshot viewer functionality in AdminPanel.tsx (lines ~464-478) currently lacks error handling when processing base64 data, which can lead to runtime crashes if invalid or malformed data is encountered.

Current Issue

• No validation of base64 data before processing
• can throw errors on invalid input
• Large payloads can cause browser hangs
• Missing error feedback to users
• URL object leaks if errors occur during processing

Proposed Solution

• Wrap base64 parsing and blob creation in try/catch blocks
• Validate base64 data exists before processing
• Add size limits for base64 data
• Provide user feedback via toast notifications on errors
• Ensure proper cleanup of object URLs in finally blocks

References

• PR: Fix/dashboard loading state #13
• Comment: Fix/dashboard loading state #13 (comment)

Files Affected

Priority

Medium - Security and user experience improvement</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Harden screenshot viewer: Add error handling for invalid base64 data #14

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