[FEATURE] Add loading skeleton cards during search

[ascender1729]

Description

Show animated skeleton placeholder cards while issues are being fetched.

Why Needed

• Better perceived performance
• Indicates content is loading
• Modern UX pattern (vs spinning loader)

Implementation Details

• Create SkeletonCard component
• Show 3-6 skeleton cards during loading
• Animate with shimmer/pulse effect
• Match actual card dimensions

Files to Create/Modify

• src/components/shared/SkeletonCard.svelte (new)
• src/components/results/ResultsContainer.svelte

Code Example

{#if isLoading}
  {#each Array(4) as _}
    <SkeletonCard />
  {/each}
{:else}
  {#each issues as issue}
    <IssueCard {issue} />
  {/each}
{/if}

Acceptance Criteria

• Skeleton cards shown during loading
• Smooth animation effect
• Matches real card layout
• Graceful transition to real content

Time Estimates

• With AI: 70 minutes
• Without AI: 450 minutes