[FEATURE] Add authentication state indicator in header

[ascender1729]

Description

Show a visual indicator (green dot/badge) when user is authenticated with GitHub.

Why Needed

• Confirms authentication status
• Visual distinction between auth/unauth states
• Reduces confusion about API rate limits
• Professional UX pattern

Implementation Details

• Check isAuthenticated state from auth store
• Show small green indicator next to title or in header
• Add tooltip showing 'Authenticated with GitHub'
• Hide indicator when not authenticated

Files to Modify

• src/components/results/ResultsContainer.svelte (header section)

Code Example

<h1 class="text-4xl font-extrabold text-white">
  IssueFlow
  {#if isAuthenticated}
    <span 
      class="inline-block w-3 h-3 bg-green-500 rounded-full ml-2"
      title="Authenticated with GitHub"
      aria-label="Authenticated"
    ></span>
  {/if}
</h1>

Acceptance Criteria

• Green dot appears when authenticated
• Dot hidden when not authenticated
• Tooltip shows 'Authenticated with GitHub'
• Accessible (aria-label)
• Positioned cleanly

Time Estimates

• With AI: 135 minutes
• Without AI: 900 minutes