Eliminate getFavicon duplication in injected script

[Copilot]

Description

Removes duplicated getFavicon function code (86 lines) from the injected script by using function serialization.

Type of Change

• ♻️ Code refactoring (no functional changes)

Changes Made

• Serialize getFavicon using .toString() and pass as argument to chrome.scripting.executeScript
• Reconstruct function in page context using eval instead of duplicating implementation
• Add explanatory comments about the serialization approach and safety considerations

The function is now maintained in one location. Updates to favicon selection logic automatically propagate to the injected script without manual synchronization.

// Before: 86 lines of duplicated getFavicon implementation inline
const results = await chrome.scripting.executeScript({
  target: { tabId: tab.id },
  func: () => {
    function getFavicon() { /* 86 lines duplicated here */ }
    // ...
  }
});

// After: Single source of truth with serialization
const getFaviconStr = getFavicon.toString();
const results = await chrome.scripting.executeScript({
  target: { tabId: tab.id },
  func: (getFaviconCode) => {
    const getFavicon = eval('(' + getFaviconCode + ')');
    // ...
  },
  args: [getFaviconStr]
});

Testing

• I have tested these changes locally
• I have tested the extension in Chrome/Edge
• I have tested the Home Assistant webhook integration (if applicable)
• I have verified that no XSS or security vulnerabilities are introduced

Screenshots (if applicable)

N/A - Internal refactoring with no UI changes

Checklist

• My code follows the existing code style
• I have performed a self-review of my changes
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings or errors
• I have tested edge cases and error conditions
• Any dependent changes have been merged and published

Related Issues

Addresses feedback from #37 (comment #37 (comment))

Additional Notes

The eval usage is safe here as we control the source code and execution occurs in the page context, not the extension context. ESLint exception is documented inline.

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