fix: resolve linting issues in memory system

- Add key to #each block in MemoryBrowserPanel (ESLint)
- Replace .last() with .next_back() for better performance (Clippy)
- Format files with Prettier

Co-Authored-By: Hikari <hikari@nhcarrigan.com>

src/lib/components/MemoryBrowserPanel.svelte

@@ -144,12 +144,14 @@
       {:else if memoryFiles.length === 0}
         <div class="empty">
           <p>No memory files found.</p>
-          <p class="hint">Memory files are created automatically as I learn from our conversations!</p>
+          <p class="hint">
+            Memory files are created automatically as I learn from our conversations!
+          </p>
         </div>
       {:else}
         <div class="panel-layout">
           <div class="file-list">
-            {#each memoryFiles as file}
+            {#each memoryFiles as file (file)}
               <button
                 class="file-item"
                 class:active={selectedFile === file}